Engineer-to-Engineer Note

a

EE-68

Technical notes on using Analog Devices DSPs, processors and development tools
Visit our Web resources http://www.analog.com/ee-notes and http://www.analog.com/processors or
e-mail processor.support@analog.com or processor.tools.support@analog.com for technical support.

Analog Devices JTAG Emulation Technical Reference
Contributed by David M. Doyle

Rev 10 – April 15, 2008

Introduction
This document provides technical information to properly design a JTAG emulator interface for Analog
Devices, Inc. (ADI) processor targets, which are all referred to as digital signal processors (DSPs) in thisdocument. For an introduction to the IEEE 1149.1 (JTAG) standard, see Appendix E: Introduction toIEEE Std. 1149.1 (JTAG) Boundary Scan.
ADI designs, manufactures, and sells several different types of JTAG emulators for use with ADI DSP
targets supporting an embedded JTAG emulator port. This document has been revised to only support thecurrent line of ADI emulators. This product line includes the HPPCI, HPUSB, and USB emulators.
Previous versions of this document supported ADI JTAG emulator legacy products such as MountainICE, Summit-ICE, Trek-ICE, Apex-ICE, and EZ-ICE. For information about JTAG emulators notsupported by this document, contact ADI’s DSP development tools technical support(processor.tools.support@analog.com) for an older version of this document that has legacy JTAG
emulator information.

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Do not use older versions of EE-68 for new target designs. Periodically, check ADI’s Web site forthe latest version of this document. Targets designed using an older version of EE-68 should only
be updated if there are problems performing JTAG emulation.
http://www.analog.com/ee-notes/

Table of Contents
Introduction ................................................................................................................................................................................................. 1
Table of Contents...................................................................................................................................................................................... 1
List of Figures .......................................................................................................................................................................................... 2
List of Tables............................................................................................................................................................................................. 2
JTAG Emulator Interface Design....................................................................................................................................................... 3
JTAG Emulator Target Header.............................................................................................................................................................. 3
Local Boundary Scan Controller....................................................................................................................................................... 3
Special Case Pin 5 BTMS .................................................................................................................................................................. 3
BTMS Pin VDDIO Auto-Detect Function ................................................................................................................................ 4
BTMS Pin Boundary Scan Function.......................................................................................................................................... 4

Copyright 2004-2008, Analog Devices, Inc. All rights reserved. Analog Devices assumes no responsibility for customer product design or the use or application ofcustomers’ products or for any infringements of patents or rights of others which may result from Analog Devices assistance. All trademarks and logos are propertyof their respective holders. Information furnished by Analog Devices applications and development tools engineers is believed to be accurate and reliable, however
no responsibility is assumed by Analog Devices regarding technical accuracy and topicality of the content provided in Analog Devices Engineer-to-Engineer Notes.

aJTAG Emulator Pod Mechanical Requirements............................................................................................................................. 5
JTAG Emulator Header Clearance Requirements................................................................................................................... 5
Target JTAG Emulator Pod Interface Design Requirements .............................................................................................. 6
JTAG Emulator Interface PCB Layout ............................................................................................................................................. 6
JTAG Emulator Power Sequence............................................................................................................................................................ 6
JTAG Emulator Pod Electrical Requirements............................................................................................................................. 6
HPPCI JTAG Emulator Automatic Voltage Sense Pod Logic ........................................................................................... 7
JTAG Emulator Pod I/O Characteristics ................................................................................................................................. 7
JTAG Emulator Pod Timing................................................................................................................................................................ 8
Conclusion ...................................................................................................................................................................................................... 9
Appendix A: Target JTAG Interface Design - Single DSP Target without Boundary Scan.......................... 10
Appendix B: Target JTAG Interface Design - Multiple DSP Target without Boundary Scan ..................... 11
Appendix C: Target JTAG Interface Design - Single DSP Target with Boundary Scan................................. 13
Appendix D: Target JTAG Interface Design - Multiple DSP Target with Boundary Scan ............................ 15
Appendix E: Introduction to IEEE Std. 1149.1 (JTAG) Boundary Scan.................................................................. 18
IEEE Std. 1149.1 (JTAG) Specification ............................................................................................................................... 18
Boundary Scan: What is It? ......................................................................................................................................................... 18
References .................................................................................................................................................................................................... 19
Document History ...................................................................................................................................................................................... 19

List of Figures
Figure 1. JTAG emulator target header interface............................................................................................................... 3
Figure 2. JTAG emulator header keep-out area...................................................................................................................... 5
Figure 3. HPPCI JTAG emulator pod dimensions...................................................................................................................... 5
Figure 4. JTAG HPUSB JTAG emulator pod dimensions.......................................................................................................... 5
Figure 5. JTAG emulator pod timing waveform ........................................................................................................................ 8
Figure 6. Single DSP target without a local boundary scan controller........................................................... 10
Figure 7. Multiple DSP target without a local boundary scan controller ...................................................... 12
Figure 8. Single DSP target with a local boundary scan controller.................................................................. 14
Figure 9. Multiple DSP target with a local boundary scan controller ............................................................. 17
Figure 10. Boundary scan implementation diagram............................................................................................................. 18

List of Tables
Table 1. JTAG emulator header signal descriptions.......................................................................................................... 4
Table 2. JTAG emulator pod I/O characteristics................................................................................................................. 7
Table 3. JTAG emulator pod timing information ................................................................................................................... 9

Analog Devices JTAG Emulation Technical Reference (EE-68)

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aJTAG Emulator Interface Design
All ADI JTAG emulators interface with the DSP
using a 14-pin JTAG emulator header. The
header provides a connection interface for the
JTAG emulator pod. The header can also be used
to connect an optional local (embedded on theuser target) boundary scan controller to the DSP
when the JTAG emulator is not attached.
All ADI JTAG emulators use a superset of theIEEE 1149.1 standard to send and receive datafrom the DSP JTAG emulation port. JTAG
emulators use an additional signal called EMU~ asa JTAG emulation status flag from the DSP. Thissignal is a vendor-specific signal, which is notpart of the IEEE 1149.1 specification.
The following pages define in detail the design
requirements for supporting ADI JTAG
emulators. This information includes functional,
electrical, and mechanical requirements forinterfacing a target design with a JTAG
emulator.

Figure 1. JTAG emulator target header interface

Local Boundary Scan Controller
Referring to Figure 1, the set of signals on the
odd-numbered side of the connector can be usedby targets which have an optional local boundary
scan controller. These signals include theboundary-scancontroller
JTAG
signals
BTMS/VDDIO, BTCK, BTDI, and BTRST~. Each ofthese signals is described in Table 1.

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If you are unfamiliar with local
boundary scan and how it may apply toyour design, see Appendix E:
Introduction to IEEE Std. 1149.1(JTAG) Boundary Scan.

JTAG Emulator Target Header
Referring to Figure 1 and Table 1, the JTAG
emulator header has 14 pins. You must supply
this header on your target to communicate with
the JTAG emulator. The JTAG emulator target
header interface is a standard dual-row 0.025”
male square-post header, employing 0.1” x 0.1”
spacing, with a minimum post length of 0.235”.
Pin 3 of the JTAG emulator cable header iskeyed to prevent accidental insertion of the podwith the target backwards. You should clip pin 3
on your target board header to allow insertion of
the JTAG emulator cable female header.

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The JTAG emulator 14-pin female
header position 3 connects to a wire in
the JTAG cable, which returns to groundat the emulator.

Special Case Pin 5 BTMS

Pin 5 BTMS/VDDIO is a dual-purpose pin on the
HPPCI JTAG emulator. First, it allows you toroute an optional local boundary scan controller
TMS signal to the target DSP TMS signal when the
JTAG ICE is not attached to the JTAG header
and a jumper is installed between pins 5 and 6 of
the JTAG header. Second, this pin is used by the
JTAG ICE to auto detect the targets DSP I/O
voltage (VDDIO) up to 5 V. The JTAG ICE uses
the sensed voltage to establish input and output
voltage levels for the DSP JTAG signals. Pull
this pin up to VDDIO using a 4.7-KΩ resistor. Do
not connect it directly to the VDDIO plane.

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Analog Devices JTAG Emulation Technical Reference (EE-68)

Only the HPPCI JTAG emulator
supports automatic voltage sensing withpin 5. The USB and HPUSB JTAG
emulator’s pin 5 only supports the BTMS
functionality.

Page 3 of 20

aPin

SignalDescription

Emulator

Target1

GND

Digital ground

Passive

Passive

2

EMU~

JTAG emulation flag

Input

Output {open drain} {active
low}{active low}
3

KEY

Header alignment position -- pin must be clipped ontarget header

GROUNDNo Connect

4

GND

Digital ground

Passive

Passive

5

VDDIO

Automatic voltage sense (VDDIO)

Input

Passive

or

or

BTMS

or
OutputTarget local boundary scan controller
JTAG TAP test mode select

6

TMS

JTAG TAP test mode selectOutput

Input

7

BTCK

Target local boundary scan controller JTAG TAP testclock

No Connect

Output8

TCK

JTAG TAP test clock

OutputInput

9

BTRST~

Target local boundary scan controller

No Connect

Output

JTAG TAP test reset{active low}

10

TRST~

JTAG TAP test reset

OutputInput {active low}

11

BTDI

Target local boundary scan controller JTAG TAP test
data inNo Connect

Output12

TDI

JTAG TAP test data in

Output

Input

13

GND

Digital ground

Passive

Passive

14

TDO

JTAG TAP test data out

Input

OutputTable 1. JTAG emulator header signal descriptions
BTMS Pin VDDIO Auto-Detect Function

The HPPCI JTAG emulator can automaticallysense a DSP IO voltage (VDDIO) up to 5 V. The
HPPCI JTAG emulator uses the VDDIO voltage it
senses from the BTMS/VDDIO pin to adjust the
JTAG emulator interface input signal thresholds
and output signal drive levels to those shown in
Table 2. You must pull pin 5 (BTMS/VDDIO) up to
the DSP I/O voltage (VDDIO) with a 4.7-KΩ
resistor when using the HPPCI JTAG emulator.
When using the HPUSB and USB JTAG
emulators which do not support VDDIO autosensing, you can connect pin 5 directly to thetarget local boundary scan controller BTMS signal
without any pull-up resistor required.

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VDDIO is the target DSP I/O voltage

supply, not the DSP core voltage supply.
Ensure that you connect VDDIO to thecorrect voltage plane when using the
HPPCI VDDIO auto-sense function.

BTMS Pin Boundary Scan Function

Pin 5 can be used to route an optional local
boundary scan controller TMS signal to the target
DSP TMS signal when the JTAG ICE is not
attached to the JTAG header and a jumper is

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 4 of 20

ainstalled between pins 5 and 6 of the JTAG
header.
You may connect an HPUSB or USB JTAG
emulator to a target designed for the HPPCIJTAG emulator with the VDDIO auto-sensing
logic. The HPUSB or USB JTAG emulator does
not connect pin 5 back at the emulator, so thetarget or emulator will not be harmed. The
voltage thresholds for your target when using the
HPUSB or USB JTAG emulators are set
manually by the user in the VisualDSP++®
Session Wizard.

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When using the HPPCI JTAG emulator,
you need to control the BTMS signal atpin 5 so that it is not being driven by the
local boundary scan controller when the
JTAG ICE is attached to the header.
Failure to isolate the BTMS signal when
the JTAG ICE is connected could resultin unpredictable behavior by the JTAGICE due to possible incorrect voltage
sensing on pin 5. As shown in Figure 8
and Figure 9, you can isolate the BTMS
signal using a jumper or a buffer. Whenusing a buffer, its output must be
disabled when the JTAG ICE isconnected.

Figure 2. JTAG emulator header keep-out area

0.20"

0.28"

0.43"

ANALOGDEVICES

0.29"
0.20"
0.70"

1.19"

Figure 3. HPPCI JTAG emulator pod dimensions

JTAG Emulator Pod MechanicalRequirements
This
sectionexplainsthemechanicalspecifications for the JTAG emulator pod.
JTAG Emulator Header Clearance Requirements

Provide a clearance of at least 0.30” and 0.10”
around the length and width of the header. Refer
to Figure 2 for information about the pod
connector keep out area.

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Allow for height clearance above theheader for attaching and detaching the
JTAG emulator cable from your target.

Figure 4. JTAG HPUSB JTAG emulator pod
dimensions

Refer to Figure 3 for height clearance restriction
information regarding the HPPCI JTAG emulator
cable. Refer to Figure 4 for any height clearance
restriction information for the HPUSB and USB
JTAG emulators.

Analog Devices JTAG Emulation Technical Reference (EE-68)

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aTarget JTAG Emulator Pod
Interface Design Requirements
This section defines how to design the JTAG
emulator pod interface for different target
platforms. The targets include single or multiple
DSP targets with or without local boundary scan
logic.
Refer to the following Appendix sections of thisdocument regarding the JTAG emulator pod
interface design requirements for the type oftarget you are designing.
Appendix A: Target JTAG Interface Design Single DSP Target without Boundary ScanAppendix B: Target JTAG Interface Design Multiple DSP Target without Boundary ScanAppendix C: Target JTAG Interface Design Single DSP Target with Boundary ScanAppendix D: Target JTAG Interface Design Multiple DSP Target with Boundary Scan

JTAG Emulator Power SequenceYour JTAG emulator should be powered on, andconnected to a host PC, prior to attaching it to atarget JTAG emulator header. All ADI highperformance JTAG emulator products can be
attached or removed from a powered “hot” target
without any power restrictions.

[

Avoid emulation errors by ensuring thatthe emulation software is not started or
executing when power is not applied tothe target, or when attaching the JTAG
emulator to a target with or without
power.

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You must install a 4.7-KΩ pull-downresistor on the TRST~ net going to the
DSP per appendixes A through D,
except for targets that use boundary scan
logic AND do not control the TRST/~
signal.
For targets that use boundary scan logic
AND do not control the TRST~ signal,
do not pull down the TRST~ signal. Useof this resistor could prevent theboundary scan logic from moving thetap. A jumper should be installed for the
TRST~, signal across the JTAG emulator
header TRST~ and BTRST~ pins before
applying power to the target. Install thisjumper whenever the JTAG emulator is
not attached to the JTAG emulator
header after power has been applied tothe target. This jumper prevents the
JTAG TAP in the DSP from getting“lost” in an un-recoverable state.

JTAG Emulator Interface PCB
LayoutTreat all JTAG emulator signals (TCK, TMS, TDI,
TDO, EMU~, and TRST~) as critical route signals.
Pay special attention when routing these signals
on your target. Specify a controlled impedance
requirement between 50 Ω and 75 Ω. Minimize
cross-talk and inductance on these signal lines byusing a solid ground plane and routing the JTAG
emulator signals away from high-frequency nets,
especially clock lines. Keep these routes as short
as possible, and equal in length when possible.
These lines must be clean. You may need toprovide series terminations for very long TDO andEMU~ routes. See appendixes A through D for
information regarding series terminations.

JTAG Emulator Pod Electrical
Requirements
This section explains the electrical specifications
for the JTAG emulator pod.

Analog Devices JTAG Emulation Technical Reference (EE-68)

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a
HPPCI JTAG Emulator Automatic Voltage Sense
Pod Logic

The HPPCI JTAG emulator pod uses pin 5(BTMS/VDDIO) of the JTAG emulator header toautomatically sense the target I/O voltage. The
voltage sensing logic controls which voltage
threshold values the JTAG emulator uses for
JTAG signals received from the target. The
voltage sensing logic also sets the drive levels for
JTAG signals sent to the target.
Your target DSP IO voltage (VDDIO) may or may
not be the same voltage used by the DSP core.
Ensure that you are using the correct DSP supply
voltage for VDDIO when configuring your target
for the HPPCI JTAG emulator automatic voltage
sense. You must pull the signal up to the correct
Pin

JTAG
Emulator

voltage plane with a 4.7-KΩ resistor. Do notconnect the BTMS/VDDIO pin directly to the VDDIO
voltage plane. See Appendixes A through D for
more information regarding the BTMS/VDDIO pin.
JTAG Emulator Pod I/O Characteristics

The JTAG emulator pod is tolerant up to 5V DC.
It will work with all Analog Devices JTAG
family DSPs with JTAG I/O voltages of 5 V,
3.3 V, 2.5 V, and 1.8 V. The pod will drive 5-V
targets with 3.3-V logic levels, which are wellwithin the 5-V logic threshold requirements.
Table 2 includes all the I/O characteristics for the
JTAG emulator pod.

VDDIO

Cin

Cout

VIH

VIL

VOH

VOL

IOL

IOH

(VDC)

(pF)

(pF)

(VDC)

(VDC)

(VDC)

(VDC)

(mA)

(mA)

6

2.0

0.8

-

-

-

-

Signal2

EMU~

5 / 3.3

6TMS

5 / 3.3

6.5

-

-

2.3

0.7

12

12

8

TCK

5 / 3.3

6.5

-

-

2.3

0.7

12

12

10

TRST~

5 / 3.3

6.5

-

-

2.3

0.7

12

12

12

TDI

5 / 3.3

6.5

-

-

2.3

0.7

12

12

14

TDO

5 / 3.3

6

2.0

0.8

-

-

-

-

2

EMU~

2.5

6

1.7

0.7

-

-

-

-

6

TMS

2.5

6.5

-

-

1.8

0.6

8

8

8

TCK

2.5

6.5

-

-

1.8

0.6

8

8

10

TRST~

2.5

6.5

-

-

1.8

0.6

8

8

12

TDI

2.5

6.5

-

-

1.8

0.6

8

8

14

TDO

2.5

6

1.7

0.7

-

-

-

-

2

EMU~

1.8

6

1.2

0.6

-

-

-

-

6

TMS

1.8

6.5

-

-

1.3

0.5

4

4

8

TCK

1.8

6.5

-

-

1.3

0.5

4

4

10

TRST~

1.8

6.5

-

-

1.3

0.5

4

4

12

TDI

1.8

6.5

-

-

1.3

0.5

4

4

14

TDO

1.8

1.2

0.6

-

-

-

-

6

Table 2. JTAG emulator pod I/O characteristics

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 7 of 20

aJTAG Emulator Pod TimingThis section details important timing information
regarding JTAG signals at the target JTAG
emulator header. Figure 5 diagrams switching
and timing relationships for JTAG signals at thetarget JTAG emulator header.
Table 3 defines switching parameters for the
JTAG emulator output signals (TCK, TMS, TDI,

and TRST~), and setup and hold requirements for
JTAG emulator input signals (TDO, and EMU~).
Table 3 also defines the frequency of operation
range for high performance JTAG emulator
products. The table parameter reference numbers
maps to the timing diagram reference numbers
shown in Figure 5.

Figure 5. JTAG emulator pod timing waveform

Use this information to determine your target’s
maximum routing lengths, net loading, and load
capacitance which can be tolerated for JTAG
emulation signal routes.
The maximum frequency numbers shown in
Table 3 are only guaranteed when your target
meets the setup and hold requirements defined inTable 3. When calculating your setup and holdmargins, be sure to include the TDO and EMU~
delay parameters from the target DSP data sheet.
If your target does not meet the setup and holdrequirements specified in Table 3, you will haveto operate the JTAG emulator at a lower
frequency for reliable performance.

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If you cannot operate the JTAG
emulator using the lowest available
frequency, check your target forincorrect wiring, or redesign your target
to reduce delays. Try to reduce trace
lengths, reduce electrical loads, and use
faster buffers.

The setup and hold time requirements are basedon the worst-case maximum delay of the JTAG
emulator hardware. Typically, the setup and holdtime requirements will be considerably smaller

than the values in the table. If you have acomplex JTAG emulation path with longpropagation delays, perform a timing analysis on
your target’s JTAG paths. Use this analysis todetermine whether your target JTAG emulation
paths have sufficient timing margin to operate at
the desired JTAG TCK frequency.
When performing a timing analysis, the timing
margin must be a positive number. As a generalrule, the desired margin should be at least 10% of
a full TCK clock period. However, be aware when
you are doing your analysis, the delay numbers
given are based on worst-case delay. Typically,
logic will tend to run somewhere in the middle
between minimum and maximum delay, although
this cannot be guaranteed. If your margin isnegative, but very close (< 1 ns), you may want
to try using typical numbers in your analysis tosee whether you still have a negative margin.
If you still calculate a negative margin using
typical values, try selecting a slower TCK
frequency if available, or make changes to yourtarget to reduce the JTAG emulator path delays.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 8 of 20

a#Parameter

Product

Frequency

Description

Min. Freq.
(ns)Max. Freq.
(ns)

1

tcTCK

HPPCI

10↔50 MHzTCK period

19.9

100.1

1

tcTCK

HPUSB

5↔50 MHzTCK period

19.9

200.1

1

tcTCK

USB

10 MHz

TCK period

99.1

100.1

2

twTCKH

HPPCI

10↔50 MHzTCK high pulse width

9.95

50.05

2

twTCKH

HPUSB

5↔50 MHzTCK high pulse width

9.95

100.05

2

twTCKHUSB

10 MHz

TCK high pulse width

49.95

50.05

3

twTCKL

HPPCI

10↔50 MHzTCK low pulse width

9.95

50.05

3

twTCKL

HPUSB

5↔50 MHzTCK low pulse width

9.95

100.05

3

twTCKLUSB

10 MHz

TCK low pulse width

49.95

50.05

4

tdTMS

HPPCI

10↔50 MHz

Delay TMS/TDI/TRST~ from TCK ↓

3

4

tdTMS

HPUSB

5↔50 MHz

Delay TMS/TDI/TRST~ from TCK ↓

3

4

tdTMS

USB

10 MHzDelay TMS/TDI/TRST~ from TCK ↓3

5

tsuTDOHPPCI

10 MHzSetup time TDO/EMU~ to TCK ↑

14.1

5

tsuTDO

HPPCI

25 MHzSetup time TDO/EMU~ to TCK ↑1

5

tsuTDOHPPCI

33 MHzSetup time TDO/EMU~ to TCK ↑8.4

5

tsuTDOHPPCI

50 MHzSetup time TDO/EMU~ to TCK ↑9.9

5

tsuTDO

HPUSB

5-50 MHz

Setup time TDO/EMU~ to TCK ↑2

5

tsuTDOUSB

10 MHzSetup time TDO/EMU~ to TCK ↑

2

6

thTDO

HPPCI

10-50 MHz

Hold time TDO/EMU~ from TCK ↑

0

6

thTDO

HPUSB

5-50 MHz

Hold time TDO/EMU~ from TCK ↑

0

6

thTDO

USB

10 MHzHold time TDO/EMU~ from TCK ↑0

Table 3. JTAG emulator pod timing information

Conclusion
The recommendations in this document shouldmake designing the JTAG emulation interface
for your target straight forward. Having a welldesigned JTAG emulator interface on your target
will allow you to rapidly begin development andtesting your application, instead of spending
valuable time debugging the JTAG emulation
port. Check the ADI DSP Tools Web site
periodically for updates to this document.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 9 of 20

aAppendix A: Target JTAGInterface Design - Single DSP
Target without Boundary Scan

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This section describes how to design the JTAG
emulator pod interface for single DSP targets
without a local boundary scan controller.
As shown in Figure 6, single DSP targets without
a local boundary scan controller, or do notinclude the DSP in a local boundary scan
controller chain, should tie all boundary scan
pins (except for pin 5) to ground when using the
HPPCI JTAG emulator. Pin 5, the BTMS/VDDIO
signal, is required by the HPPCI JTAG emulator
pod to automatically sense the DSP I/O voltage(VDDIO).

Figure 6 shows series terminating
resistors for the TDO and EMU~ signals
going to the JTAG emulator. These
resistors are optional. Use terminators if
the TDO or EMU~ routes are longer than
6 inches between the DSP and the JTAG
emulator header.

Single DSP targets with routing distances
between the JTAG emulator header and the DSPof less than six (6) inches do not requirebuffering.

The terminator resistor value is generally equal
to the impedance of the printed circuit board(ZPCB) minus the output impedance of the TDO or
EMU~ signal I/O driver (ZDriver). Initially, set these
resistors to zero ohms. Change the value of thetermination resistance ZTerminator, to ZPCB minus
ZDriver if signal integrity problems are observed
when using the JTAG emulator. Tuning thetermination resistor value to something slightly
less than or greater than ZTerminator may berequired, depending on the condition of thesignals. Place the termination resistors as close to
the DSP as possible.

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Buffer your target if the worst-caseroute distance between the JTAG
emulator header and the DSP is greaterthan six (6) inches, regardless of thenumber of DSPs in the scan chain path.

Previous versions of this document
called for pull-up resistors on TMS, TCK,
and TDI. The strong drive strength of the
CMOS buffers used in the emulator
makes this unnecessary.

Figure 6 shows the connections between the
JTAG emulator header and the DSP for a single
DSP target without a local boundary scan
controller.

Figure 6. Single DSP target without a local boundary scan controller
Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 10 of 20

aAppendix B: Target JTAGInterface Design - Multiple DSP
Target without Boundary Scan

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This section describes how to design the JTAG
emulator pod interface for multiple DSP targets
without a local boundary scan controller.
As shown in Figure 7, targets with multiple
DSPs in the chain and without a local boundary
should tie all boundary scan pins (except pin 5)
to ground when using the HPPCI JTAG
emulator. Pin 5, the BTMS/VDDIO signal, is
required by the HPPCI JTAG emulator pod toautomatically sense the DSP I/O voltage(VDDIO).
As shown in Figure 7, targets with more than one
DSP in the scan path, which do not use a local
boundary scan controller, require buffering.
Figure 7 shows the connections between the
JTAG emulator header and buffers for a multiple
DSP target without a local boundary scan
controller.
For 5-V targets, buffer the TCK signal with alow-skew, high fan-out, minimal input-to-output
delay, dual 1-to-5 clock driver type
IDT49FCT805 (or equivalent), and buffer the
TMS, TDI, TRST~, TDO, and EMU~ signals with atype 74AC11244 buffer (or equivalent).
For 3.3-V low-voltage targets, buffer the TCK
signal with a low-skew, high fan-out, minimal
input-to-output delay, dual 1-to-5 clock driver
type IDT49FCT3805E (or equivalent), andbuffer the TMS, TDI, TRST~, TDO, and EMU~
signals with a type 74AVC16244 buffer (orequivalent).
For 2.5-V / 1.8-V very low voltage targets,
buffer the TCK signal with a low-skew, high fanout, minimal input-to-output delay, single 1-to-5
clock driver type IDT5T9050 (or equivalent),
and buffer the TMS, TDI, TRST~, TDO, and EMU~
signals with a type 74AVC16244 buffer (orequivalent).

Figure 7 shows series terminating
resistors for the TDO and EMU~ signals
going to the JTAG emulator. These
resistors are optional. Use terminators if
the TDO or EMU~ routes between thebuffers and the JTAG emulator header
are longer than 6 inches.

The terminator resistor value is generally equal
to the impedance of the printed circuit board(ZPCB) minus the output impedance of the TDO or
EMU~ signal I/O driver (ZDriver). Initially, set these
resistors to zero ohms. Change the value of thetermination resistance ZTerminator, to ZPCB minus
ZDriver if signal integrity problems are observed
when using the JTAG emulator. Tuning thetermination resistor value to something slightly
less than or greater than ZTerminator may berequired, depending on the condition of thesignals. Place the termination resistors as close to
the DSP as possible.

L

To minimize signal skew, ensure thatbuffers for the TMS, TDI, TRST~, TDO,
and EMU~ signals come from a single
package. For TCK signals, use a driverwith a high fan-out. The drivers shouldcome from a single dedicated packagethat is not used by other TMS, TDI,TRST~, TDO, or EMU~ signals.

Route all traces between the JTAG emulator
header and the DSP as a group, using equal
lengths when possible. Provide good crosstalk
isolation from other signal nets especially clocks.
Limit the number of loads (DSPs) for the TMS,
TRST~, and EMU~ buffered signals to eight (8).
Limit the number of loads for the TCK bufferedsignals to one (1). Additional loads (DSPs)
should use another buffer to support up to eight(8) more devices.

L

Analog Devices JTAG Emulation Technical Reference (EE-68)

Previous versions of this document
called for pull-up resistors on TMS, TCK,
and TDI. The strong drive strength of the
CMOS buffers used in the emulator
makes this unnecessary.

Page 11 of 20

a

EMU

TRST

TDO

TMS

TDI

TCK

EMU

TRST

TDO

TMS

TDI

header and buffers. If this is not possible, try
adding jumpers to reduce the number of devices
in one chain at a time for debug purposes. Pay
special attention to PCB routing to minimize
transmission line effects.

TCK

Using more than sixteen (16) physical devices in
one scan chain is not recommended. The best
approach for large numbers (>16) of physicaldevices is to break the chain into smaller
independent chains, each with its own JTAG

Figure 7. Multiple DSP target without a local boundary scan controller

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 12 of 20

athe local boundary scan controller and
the JTAG emulator are not being used.
Figure 8 shows how TRST~ should becontrolled when the target uses a local
boundary scan controller.

Appendix C: Target JTAGInterface Design - Single DSP
Target with Boundary Scan
This section describes how to design the JTAG
emulator pod interface for single DSP targets
with a local boundary scan controller.
Single DSP targets with local boundary scan
controller logic should connect the local
boundary scan signal pins to the JTAG emulator
header pins shown in Figure 8.
If your target has an optional local boundary scan
controller, and you attach a HPPCI JTAG
emulator, you will need to isolate the BTMS signal
from the BTMS/VDDIO voltage pin before starting
the emulator software. Referring to Figure 8,
during JTAG emulation you can isolate pin 5 on
the HPPCI JTAG emulator header from the local
boundary scan controller logic using a jumper orthree-state buffer.

L

You must provide a method to isolate
the BTMS signal on your target from the
BTMS/VDDIO pin on the JTAG emulator
header when the HPPCI JTAG emulator
is connected. Isolation must be effective
before the HPPCI JTAG emulator
software is invoked. This isolation will
prevent the local boundary scan
controller BTMS signal from confusing
the automatic voltage sensing logic in
the HPPCI JTAG emulator pod.

Connections are made between the local
boundary scan controller and the DSP by
installing or removing jumpers between the local
boundary scan controller JTAG signals and the
DSP JTAG emulation signals. The local
boundary scan signals include BTMS, BTCK, BTDI,
and BTRST~. DSP JTAG emulation signals TMS,
TCK, TDI, and TRST~ connect to local boundary
scan signals using jumpers on the JTAG
emulator header shown in Figure 8.

L

TRST~ must be pulsed low at power-up

when using a local boundary scan
controller, and should be kept low whenIf your target has a local boundary scan
controller and your target does not control the
BTRST~ signal, you will need to control the
BTRST~ signal with additional logic. Thisadditional logic must guarantee that the BTRST~
signal is only pulsed low during power-on reset.
It should be driven high all other times duringlocal boundary scan. This will prevent holding
the BTRST~ signal low continuously during local
boundary scans.
Keep the DSP TAP constantly in reset with the
BTRST~ signal forced to ground with a jumper orpull-down resistor to prevent the DSP fromexecuting a local boundary scan.

L

The 4.7-KΩ pull-down resistor on
TRST~ shown in Figure 8 should not be
used for targets which have a local
boundary scan controller and do not
drive TRST~. The DSP JTAG TAP will
be kept constantly in reset when using apull-down resistor if it cannot be
overdriven.

Figure 8 shows the connections between the
JTAG emulator header and the DSP for a single
DSP target with a local boundary scan controller.

L

Jumpers can be substituted with zero
ohm resistors on production boards. If
you plan to use the same board revision
for debugging and production, design
your target with a dual footprint. The
dual footprint should accommodate theheader described in Figure 1 for debug
boards, and surface mount resistors for
production boards.

Single DSP targets with routing distances
between the JTAG emulator header and the DSPof less than six (6) inches do not requirebuffering.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 13 of 20

aL

Buffer your target if the worst-caseroute distance between the JTAG
emulator header and the DSP is greaterthan six (6) inches, regardless of thenumber of DSPs in the scan chain path.

L

Figure 8 shows series terminating
resistors for the TDO and EMU~ signals
going to the JTAG emulator. These
resistors are optional. Use terminators if
the TDO or EMU~ routes are longer than
6 inches between the DSP and the JTAG
emulator header.

The terminator resistor value is generally equal
to the impedance of the printed circuit board(ZPCB) minus the output impedance of the TDO or
EMU~ signal I/O driver (ZDriver). Initially, set these
resistors to zero ohms. Change the value of thetermination resistance ZTerminator, to ZPCB minus
ZDriver if signal integrity problems are observed
when using the JTAG emulator. Tuning thetermination resistor value to something slightly
less than or greater than ZTerminator may berequired, depending on the condition of thesignals. Place the termination resistors as close to
the DSP as possible.

L

Previous versions of this document
called for pull-up resistors on TMS, TCK,
and TDI. The strong drive strength of the
CMOS buffers used in the emulator
makes this unnecessary.

Target DSP VDDIO
Buffer Enable Logic

BTMSOE
4.7K

GND
no pin (key)BTMS/VDDIOBoundary Scan Controller
Boundary Scan Controller
Power Up Reset Logic
Boundary Scan Reset Logic

PONRST

BTCK
BTRST

1

2

3

4

GND

5

6

TMS

7

8

9

10

11

12

13

14

EMU

Target DSP

Target DSP

TCKTarget DSP

TRSTTarget DSP

BSCRST
Boundary Scan Controller

BTDI
GND

TDI

Target DSP

TDOTarget DSP
4.7K

Figure 8. Single DSP target with a local boundary scan controller

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 14 of 20

aAppendix D: Target JTAGInterface Design - Multiple DSP
Target with Boundary Scan
This section describes how to design the JTAG
emulator pod interface for multiple DSP targets
with a local boundary scan controller.
Multiple DSP targets with local boundary scan
controller logic should connect the local
boundary scan signal pins to the JTAG emulator
header pins shown in Figure 9.

L

Jumpers can be substituted with zero
ohm resistors on production boards. If
you plan to use the same board revision
for debugging and production, design
your target with a dual footprint. The
dual footprint should accommodate theheader described in Figure 1 for debug
boards, and surface mount resistors for
production boards.

If your target has an optional local boundary scan
controller, and you attach a HPPCI JTAG
emulator, you will need to isolate the BTMS signal
from the BTMS/VDDIO voltage pin before starting
the emulator software. Referring to Figure 9
during JTAG emulation, you can isolate pin 5 on
the HPPCI JTAG emulator header from the local
boundary scan controller logic using a jumper orthree-state buffer.

L

You must provide a method to isolate
the BTMS signal on your target from the
BTMS/VDDIO pin on the JTAG emulator
header when the HPPCI JTAG emulator
is connected. Isolation must be effective
before the HPPCI JTAG emulator
software is invoked. This isolation will
prevent the local boundary scan
controller BTMS signal from confusing
the automatic voltage sensing logic in
the HPPCI JTAG emulator pod.

Connections are made between the local
boundary scan controller and the DSP by
installing or removing jumpers between the local
boundary scan controller JTAG signals and the

DSP JTAG emulation signals. The local
boundary scan signals include BTMS, BTCK, BTDI,
and BTRST~. DSP JTAG emulation signals TMS,
TCK, TDI, and TRST~ connect to local boundary
scan signals using jumpers on the JTAG
emulator header shown in Figure 9.

L

TRST~ must be pulsed low at power-up

when using a local boundary scan
controller, and should be kept low when
the local boundary scan controller and
the JTAG emulator are not being used.
Figure 9 shows how TRST~ should becontrolled when the target uses a local
boundary scan controller.

If your target has a local boundary scan
controller and your target does not control the
BTRST~ signal, you will need to control the
BTRST~ signal with additional logic. Thisadditional logic must guarantee that the BTRST~
signal is only pulsed low during power-on reset.
It should be driven high all other times duringlocal boundary scan. This will prevent holding
the BTRST~ signal low continuously during local
boundary scans.
Keeping the DSP TAP constantly in reset with
the BTRST~ signal forced to ground with a jumperor pull-down resistor will prevent the DSP fromexecuting a local boundary scan.

L

The 4.7-KΩ pull-down resistor on
TRST~ shown in Figure 9 should not be
used for targets that have a local
boundary scan controller and do not
drive TRST~. The DSP JTAG TAP will
be kept constantly in reset when using apull-down resistor if it cannot be
overdriven.

As shown in Figure 9, targets with more than one
DSP in the scan path, which do use a local
boundary scan controller, require buffering.
Figure 9 shows the connections between the
JTAG emulator header and buffers for a multiple
DSP target with a local boundary scan controller.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 15 of 20

a
For 5-V targets, buffer the TCK signal with a lowskew, high fan-out, minimal input-to-output
delay, dual 1-to-5 clock driver type
IDT49FCT805 (or equivalent), and buffer the
TMS, TDI, TRST~, TDO, and EMU~ signals with atype 74AC11244 buffer (or equivalent).
For 3.3-V low-voltage targets, buffer the TCK
signal with a low-skew, high fan-out, minimal
input-to-output delay, dual 1-to-5 clock driver
type IDT49FCT3805E (or equivalent), andbuffer the TMS, TDI, TRST~, TDO, and EMU~
signals with a type 74AVC16244 buffer (orequivalent).
For 2.5-V / 1.8-V very low voltage targets, buffer
the TCK signal with a low-skew, high fan-out,minimal input-to-output delay, single 1-to-5
clock driver type IDT5T9050 (or equivalent),
and buffer the TMS, TDI, TRST~, TDO, and EMU~
signals with a type 74AVC16244 buffer (orequivalent).

L

Figure 9 shows series terminating
resistors for the TDO and EMU~ signals
going to the JTAG emulator. These
resistors are optional. Use terminators if
the TDO or EMU~ routes between thebuffers and the JTAG emulator header
are longer than 6 inches.

The terminator resistor value is generally equal
to the impedance of the printed circuit board(ZPCB) minus the output impedance of the TDO or
EMU~ signal I/O driver (ZDriver). Initially, set these
resistors to zero ohms. Change the value of thetermination resistance ZTerminator to ZPCB minus
ZDriver if signal integrity problems are observed
when using the JTAG emulator. Tuning thetermination resistor value to something slightly
less than or greater than ZTerminator may berequired, depending on the condition of thesignals. Place the termination resistors as close to
the DSP as possible.

L

To minimize signal skew, ensure thatbuffers for the TMS, TDI, TRST~, TDO,
and EMU~ signals come from a single
package. For TCK signals, use a driverwith a high fan-out. The drivers shouldcome from a single dedicated packagethat is not used by other TMS, TDI,TRST~, TDO, or EMU~ signals.

Route all traces between the JTAG emulator
header and the DSP as a group, using equal
lengths when possible. Provide good crosstalk
isolation from other signal nets especially clocks.
Limit the number of loads (DSPs) for the TMS,
TRST~, and EMU~ buffered signals to eight (8).
Limit the number of loads for the TCK bufferedsignals to one (1). Additional loads (DSPs)
should use another buffer to support up to eight(8) more devices.

L

Previous versions of this document
called for pull-up resistors on TMS, TCK,
and TDI. The strong drive strength of the
CMOS buffers used in the emulator
makes this unnecessary.

Using more than sixteen (16) physical devices in
one scan chain is not recommended. The best
approach for large numbers (>16) of physicaldevices is to break the chain into smaller
independent chains, each with its own JTAG
header and buffers. If this is not possible, try
adding jumpers to reduce the number of devices
in one chain at a time for debug purposes. Pay
special attention to PCB routing to minimize
transmission line effects.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 16 of 20

EMU

TDO

TRST

TMS

TDI

TCK

EMU

TRST

TDO

TMS

TDI

TCK

a

Figure 9. Multiple DSP target with a local boundary scan controller

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 17 of 20

aAppendix E: Introduction toIEEE Std. 1149.1 (JTAG)
Boundary Scan

include the boundary scan cells for all or some ofa device’s pins (user defined) which is connected
to other devices (user defined) on the PCB.

This section is a brief introduction to the IEEE
1149.1 (JTAG) specification and the concept ofBoundary Scan for customers who may be
unfamiliar with these topics.
IEEE Std. 1149.1 (JTAG) Specification

As printed circuit boards became very dense withcomplex fine pitched components in PGA andBGA packages, traditional testing methods using
bed of nails and in-circuit tests became very
difficult if not impossible. A new method needed
to be developed to allow testing these complex
dense PCBs. To solve this problem, in the 1980s
the Joint Test Action Group (JTAG) developed
the IEEE Std. 1149.1 standard utilizing
Boundary-scan for testing connections on printed
circuit boards at the device pin level. The
standard was ratified, adopted and first
introduced in 1990. Several subsequent revisions
to the specification have been adopted including
in 1993 revision 1149.1a, and in 1994 a
supplement to the specification for a boundary
scan descriptive language (BSDL) was
introduced. Companies which integrated theIEEE Std. 1149.1 standard into their products(ICs) for board and component testing, havegone further using JTAG for programming
FPGAs, downloading micro-code, and in-circuit
emulation, etc.
Boundary Scan: What is It?

Boundary scan provides a method for testing
interconnects on a PCB without having to use
physical probes like a bed of nails. By using
internal boundary scan cells with multiplexing
and latching capabilities, data can be shifted inand out of device interconnects in a serial format.
Each boundary scan cell using its own
multiplexer and latch logic is connected to a
device pin, and all boundary scan cells areconnected forming a serial chain. The chain will

Figure 10. Boundary scan implementation diagram

Figure 10 shows a diagram of how a part
implementing IEEE Std. 1149.1 would connect
the individual boundary scan cells, and the JTAG
controller logic. The pins TDI, TCK, TMS, TDO, andoptional TRST~ provide the test access port
(TAP) for shifting (TCK) data in (TDI) and dataout (TDO) controlled by (TMS). The external
device which drives the TCK, TMS, and TDI pins
can also reset the TAP controller by driving theoptional TRST~ pin. Data is returned to theexternal device controlling the operation of the
TAP with the TDO pin.
Along with boundary scan operations, Analog
Devices uses the TAP controller to accessdedicated internal registers with JTAG scan cells
to shift data in and out of the DSP, providing aport for emulation. Analog Devices does include
the optional TRST~ pin in all their current DSP
JTAG TAP logic and also uses a dedicatedemulation control pin (EMU~) which is notdefined as part of the IEEE Std. 1149.1 standard.
If you desire more information on how the IEEE
Std. 1149.1 standard works, you can visit their
Web site at http://standards.ieee.org/.

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 18 of 20

aReferences
The IEEE 1149.1 JTAG standard is sponsored by the Test Technology Standards Committee of the IEEE
Computer Society, and published by the IEEE.
To order a copy, call IEEE at 1-800-678-4333 in the US and Canada (1-908-981-1393 outside of the US
and Canada). You can also visit the IEEE standards web site at http://standards.ieee.org/

Document History
Revision

Description

Rev 10 – April 15th, 2008
by D. Doyle

Major update with the following changes:
Corrected Note 10, switching the buffer part numbers for 5V and 3.3V
Removed Notation table, and broke up the 4 different Target types (Single or Multi DSP
with or without local boundary scan) into Appendixes A through D with individual
JTAG Interface design instructions.
Updated Figures 5, 6, 7, and 8 showing TRST/ pulled low to ground with a 4.7KΩ
resistor.
Noted the special case of not using a pull down resistor when an on-board boundary
scan controller is being used and TRST/ is not controlled.
Updated Figure 2, 3, and 4 showing the physical location of pin 1 on the probe header.
Added tables of contents, list of figures, and list of tables at beginning of document tomake navigating to target applicable document information sections easier.
Removed the requirement for jumpers or zero ohm resistors on the JTAG header fortargets that do not implement their own boundary scan controller.
Added Appendix E to provide an introduction to the IEEE Std. 1149.1 (JTAG) Standard
for customers unfamiliar with the specification.

Rev 9 – October 18th, 2004
by D. Doyle

Major update. Incremented revision code to Rev 9 due to revision system change
Removed all obsolete Legacy information. Simplified and combined drawings andtables when possible. Re-wrote most sections in more concise format

Rev 2.6 – July 9th, 2003
by D. Doyle

Updated all document discussions for the TRST~ signal and JTAG Emulation header
jumper requirements. Most sections of the document were affected. Changed keep out
clearance requirements for larger HPPCI pod.

Rev 2.5 – March 20th, 2003
by D. DoyleDivided document into discussion of Legacy ICE products and our new HPPCI ICE
product. Added HPPCI information

Rev 2.4 – December 3rd, 2002
by D. Doyle

Updated all sections and added timing information

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 19 of 20

a
Rev 2.3 – August 2001
by D. Doyle

Update to power up sections

Rev 2.2 – March 2001
by D. Doyle

Update to target connections

Rev 2.1 – August 2000
by D. Doyle

Update for 2.5 logic

Rev 2.0 – February 2000
by D. Doyle

General update

Rev 1.0 – December 1999
by D. Doyle

Initial release

Analog Devices JTAG Emulation Technical Reference (EE-68)

Page 20 of 20