Communication Protocol

RS232C
Serial Interface

CGD025D
CDG045D … CDG200D
CDG045D2 … CDG100D2

RS232Ctira49e1-b(2016-01)

1General Information

The RS232C Serial Interface permits the communication between the digital
INFICON Capacitance Diaphragm Gauge and•an INFICON Vacuum Gauge Controller (VGC series) or•

another appropriate controller.

The RS232C Serial Interface integrated in the Capacitance Diaphragm Gauge
allows to digitally transmit measurement values and information on the gauge
status as well as to make parameter settings.

CautionCaution: data transmission errors
Any attempt to simultaneously operate the gauge via the RS232C
Serial Interface and a fieldbus interface (DeviceNet or Profibus) or the
diagnostic port may result in incorrect data and data transmission
errors.
Therefore, it is inadmissible to simultaneously operate the gauge via
the RS232C Serial Interface and DeviceNet, Profibus, or the
diagnostic port.

Functional Principle

Data format

2

The RS232C Serial Interface is used in duplex operation. The gauge continuously(approximately every 20 ms) transmits a nine byte send string without request.
Instructions to the gauge are transmitted via five-byte receipt strings.
•binary•

8 data bits•

1 stop bit•

no parity bit•

no handshake

Transmission rate•

9600 BaudPin assignment•

TxD

Pin 13•RxD

Pin 14•GND
Pin 5(sensor cable connector)

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RS232C.cp

1 Interface Protocol

1.1 Send String

Structure of send string

Page No. byte
(byte No. 1)

The complete send string (frame) is nine bytes (byte 0 … 8) long. Bytes 1 … 7 form
the data string.
Byte No.

4

Measured value high byte

<value>→ "Calculation of pressure value"

5Measured value low byte

<value>67

Read command
Sensor type<value>→ "Calculation of pressure value"
Read value

8Checksum

23→ "Status byte"→ "Error byte"→ "Sensor type"→ "Synchronization"

Definition
Parameter for CDG025D with output signal 10.24 V
Parameter for CDG045D … CDG200D and CDG045D2 … CDG100D2
with output signal 10.24 V
Parameter for CDG025D with output signal 10.00 V (analog)

Bit 0Definition

01

Continuous output of measured value
Individual measured value (polling) 1)→  8, "DataTxMode". Send a read command of any parameter to the gauge forrequesting a send string.

Bit 2

Bit 1

1101

Definition
Manual setpoint setting
Zero adjust active

Bit 3

Definition0⇔1

Toggle bit, changes with every stringreceived correctly

Bit 5

Bit 400
1010

Bit 7011)

RS232C.cp

Parameter
Parameter

Error

01(2016-01)

743

Bit 6

tira49e1-bComment

Data string lengthPage No.
StatusValue1)

Value

012

4

Status byte(byte No. 2)

Function

Definition
Current pressure unit mbar
Current pressure unit Torr
Current pressure unit Pa
Definition
Standard measurement mode
Reserved for internal use
Definition
Heating 1)
Sensor temperature attained 1)

for CDG045D, CDG045D2, CDG100D, CDG100D2, CDG160D, CDG200D only3

Bit No.

Error byte(byte No. 3)

01
2
3
4
5
6
7Definition
RS232 synchronization error
Incorrect command, e.g. inadmissible address (syntax error)
Inadmissible read commandSP1 status
SP2 status
Not usedNot used
Extended error set (→ Read command "Extended Error
L-Byte and H-Byte")

No bit set → value = 0x00 = no error set

Error handling

Errors are only recorded in the error bytes as long as they persist, except for
RS232 interface errors. Errors are not acknowledged.
RS232 errors are signaled by the "toggle bit", i.e. when an RS232 error occurs, the"toggle bit" is not inverted. For checking the status of the "toggle bit", a read
operation is required, which also allows to read the error byte for detailed error
analysis.
If an "extended error" is set, it has to be read as variable by means of the "readcommand" (→ table "Variables for bytes No. 2 and 3"). After the read operation, thevariable is automatically erased.

Measurement value high/lowbytes

The measurement value is transmitted as <16 bit signed integer value>. The
pressure is calculated from bytes 4 and 5 of the send string (decimal presentation)
as follows.
p =<pressure_value> × ab

Parameter
pF.S.R._Mantissa
F.S.R._Exp<pressure_value>b(F.S.R._Exp)× F.S.R._Mantissa × 10

Description
Pressure value in selected pressure unit (→ factor "a",table "Conversion factor for pressure units")
F.S.R. factor according to "Sensor type" variable (→ "Byte
No. 7")
F.S.R. exponent according to "Sensor type" variable(→ "Byte No. 7")
Pressure measurement value, converted into decimalformatFactor for resolution (→ Table "Conversion factor forpressure units")

Conversion factor forpressure units
Page No.
Byte No. 1

2 and 344Pressureunit
Byte No. 2
bit 4, 5

F.S.R.
Mantissa
Byte Nr. 7
bit 4-7

Factor"a"

Factor"b"

0 = mbar

1.333224'0001.000032'0002 = Pa0x0
or>0x1133.3224'0000 = mbar

0x113332

26'400F.S.R. 1100 mbarxxx

xxx

32'767

CDG025D with output
signal 10.00 V

1 = Torr

Commenttira49e1-b(2016-01)

RS232C.cp

Read command(byte No. 6)

All variables in a receipt string that are addressed for reading are output on thisbyte. For variable types >1 byte, each byte (e.g. low, high, or further bytes) has tobe addressed and read individually.
Read Command L-Byte → Read Data L-Byte
Read Command H-Byte → Read Data H-Byte•

After a write operation, the value of the addressed variable is output.

•

After a reset (Power on) the software version is output on byte 6.

Sensor type(byte No. 7)

Checksum and synchronization(byte No. 8)

Bit No.
0…3

Description
F.S.R._Exp0x0

10-3

0x10x20x30x4
0x50x60x7

10-2
10-1
100101102103
104

Bit No.
4…7

Description
F.S.R._Mantissa

0x0

1.00x1
0x20x30x4

1.1
2.0
2.5
5.0

(2016-01)

RS232C.cp→ Variable "Sensor_pressure_range"

Comment→ Variable "Sensor_FSR"

The recipient (master) is synchronized by checking three bytes:
Byte No.

tira49e1-bComment

Function

Value

Comment01

Data string length
Page No.

8Checksum of bytes
No. 1 … 774320 … 255

Constant value
Constant value for CDG025D 1)
2)
Constant value for CDGxxxDx
Constant value for CDG025D 3)
Low byte of checksum 4)

1)

CDG025D with output signal 10.00 V (analog)

2)

CDG045D, CDG045D2, CDG100D, CDG100D2, CDG160D, CDG200D with output signal
10.24 V (analog)

3)

CDG025D with output signal 10.24 V (analog)

4)

Possible high bytes are ignored5Example

The example is based on the following output string:
Byte No.

01234

5678Value

72160125020669

The instrument or controller (receiver) interprets this string as follows:
Byte No.
01234
5678

1.2 Receipt String

Structure of receipt string

Value

Comment7(Set value)

2160

CDG025D with output signal 10.24 V
Pressure unit = Torr
No Error
Calculation of pressure value: Conversion
formula →  4Length ofdatastring
Page No.
StatusError
Measurement
High byte
Low byte
Read commandSensor type
Check sum

1250206169

Software version = 20 / 20 = 1.0
F.S.R.= 10+32 + 16 + 0 + 125 + 0 + 20 + 6 =169dec ≙ 00 A9hex
High order byte is ignored 
Check sum = A9hex ≙ 169dec

Commands to the gauge are transmitted in receipt strings (frames) consisting offive bytes (without <CR>). The data string is formed by bytes 1 … 3.
Byte No. Designation
012346Function

Data string length
Data
Data
Data
Checksumof bytes No. 1 … 3Value
3(constant value)→ "Service command"→ "Address byte"→ "Data byte"<value>Low byte of checksum1)

1)

Possible high bytes are ignored.

•The operation selected in byte No. 1 is addressed in byte No. 2.

•

Variables are transmitted in byte No. 3. Variables >1 byte have to betransmitted in several receipt strings (splitting).

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RS232C.cp

Service command(byte No. 1)

Description

DataComment

Read command0x00

Write command

0x10

Special services

0x40

Read command for variable according toaddress in byte No. 2
Write command for variable according toaddress in byte No. 2
Direct command (write command) without
data information, e.g. Reset, Zero adjust

Address byte
(byte No. 2)Enter the address of the variable to be read/written (→ table "Variables for bytes
No. 2 and 3").

Data byte(byte No. 3)

When a variable is written (receipt string) the content of byte No. 3 is written to thevariable addressed in byte No. 2 (→ table "Variables for bytes No. 2 and 3").
When a variable is read (send string), the value of the variable addressed in byte
No. 2 is output in byte No. 6 of the send string. The content of byte No. 3 is not
relevant for read operations.

Checksum(byte No. 4)
ExampleThe checksum is calculated from the sum of byte No. 1 to 3.

The example is based on the receipt string:
Byte No.

01234Value

30202

The instrument or controller (receiver) interprets this string as follows:
Byte No.

Designation

0

Data string
lengthServicecommand
Address byte
Data byte
Checksum1234

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Value Comment3(constant value)

0Read command

202

Filter0 + 2 + 0 = 2dec ≙ 00 02hex
High bytes are ignored Checksum = 02hex ≙ 2dec

7

Variables for bytes No. 2 and 3(read/write command)
Parameter name

Data type

DataTxMode

uint8_T / RWUnit
Filter

SP1 Level Low
SP2 Level Low

Description0

uint8_T / RW

1

uint8_T / RW

sint16_T / RW
sint16_T / RW

SP1 Level Highsint16_T / RW

SP2 Level Highsint16_T / RW

Software version

uint8_T / Ro

Calib dateuint32_T / Ro

Byte No. 22

Byte No. 3 Comment0 1)

Continued output of measured value

1

Individual output of measured value(polling)

0Pressure unit "mbar"1 1)

Pressure unit "Torr"

0 1)

Filter dynamic1

Filter time fast2

Filter time slow
Lower setpoint threshold SP1 2)

H-Byte4<value>L-Byte5<value>H-Byte6<value>L-Byte7<value>H-Byte8<value>L-Byte9<value>H-Byte10<value>L-Byte11<value>16<value>(<value> / 20) = Software Version
e.g. 20 = V1.0

17<value>Date: YY,MM,DD,HH,MMMSB

Lower setpoint threshold SP2 2)Upper setpoint threshold SP12)(hysteresis)
Upper setpoint threshold SP2(hysteresis) 2)

Byte 218<value>e.g. 0410291109 =Byte 119<value>2004-10-29 at 11:09

LSB20<value>H-Byte21<value>L-Byte22<value>H-Byte23<value>Customer DC Output Offset 3)

Zero Offset Adjust Level 3)

Zero_Adjust_Valuesint16_T / RW

DC Output Offset

sint16_T / RW

L-Byte24<value>(Base pressure offset)

Production No.

uint8_T / Ro

Byte 025<value>Production number as ASCII string(barcode)

uint8_T / Ro

Byte 126<value>(Max. 16 byte)

uint8_T / Ro…

…

...

Software date Year

Software date M/DPart No.

Remaining_Zero

uint8_T / Ro

Byte 1540<value>(Last digit: null terminator)

uint16_T / Ro

H-Byte212<value>Software version date Year in Hex
e.g. 0x2007 = 2007

L-Byte213<value>H-Byte214<value>Software version date Month in Hex
e.g. 0x03 = March

L-Byte215<value>Software version date Day in Hex
e.g. 0x19 = 19

uint8_T / Ro

Byte 0218<value>Part number as ASCII string

uint8_T / Ro

Byte 1219<value>(Max 20 byte)

uint8_T / Ro…

…

<value>e.g. 378-000

uint8_T / Ro

Byte 19237<value>(Last digit: null terminator)

sint16_T / Ro

H-Byte72<value>Max. remaining offset value

73<value>Uint16_T / Ro

L-Byte(continued)

8tira49e1-b(2016-01)

RS232C.cp

(Table "Variables for bytes No. 2 and 3 (read/write command)" completed)
Parameter name

Data type

Description

Byte No. 2

Byte No. 3

Comment

Extended error
H-Byteuint8_T / Ro

H-Byte54

Bit 0PT1000 fault 4)

Bit 1

Heater block overtemp. 4)

Bit 2Electronic overtemp. 4)

Bit 3

Zero adjust error

Bit 4

Reserve

Bit 5

Reserve

Bit 6

Reserve

Extended error
L-BytePressure range(Exponent)

Pressure range(Mantissa)

Gauge config
CDG type

RW = Read / Write

tira49e1-b

uint8_T / Ro

L-Byteuint8_T / Ro

uint8_T / Ro

uint8_T / Ro
uint8_T / Ro

55

56

57

5859

Factory setting2)

Conversion → Section 1.1, byte 6 "Read command"3)

Conversion → Section 1.1, bytes 4 and 5 "Pressure unit"

4)

CDG045D, CDG045D2, CDG100D, CDG100D2, CDG160D, CDG200D only

RS232C.cp

Reserve
Atm. pressure out of range

Bit 1

Temperature out of range

Bit 2

Reserve

Bit 3

Reserve

Bit 4Cal. mode wrong

Bit 5

Pressure underflow

Bit 6

Pressure overflow

Bit 7

Zero adjust warning

0F.S.R. = E-3

1

F.S.R. = E-2

2

F.S.R. = E-1

3

F.S.R. = E 0

4

F.S.R. = E+1

5

F.S.R. = E+2

6

F.S.R. = E+3

7

F.S.R. = E+40

Mantissa = 1.01

Mantissa = 1.12Mantissa = 2.03

Mantissa = 2.54

Mantissa = 5.05Mantissa = 1.146Mantissa = 3.0

0= Analog out 0 … 10.24 V

1= Analog out 1 … 9 V

0= CDG025D

1= CDG045D, CDG045D2

2= CDG100D, CDG100D2

3= CDG160D

4= CDG200D

Ro = Read only1)(2016-01)

Bit 7
Bit 09

Variables for bytes No. 2 and 3(special services)
Parameter name

Data type

RESET

uint8_T / W

Description

Byte No. 20Byte No. 3 Comment0Power reset: Starts continuouspressure output

RESET Factory

uint8_T / W

10Factory reset: Sets factory configuration

Zero_adjustuint8_T / W

2–Starts zero offset adjustment<data_value> × ab

× F.S.R._Mantisse × 10(F.S.R._Exp)

W = Write

Description of variables
Setpoint_level xy

Setpoint_level xy =Parameter1)

Setpoint_level xy

Zero_Adjust_Value

Description
Setpoint threshold in the selected pressure unit.

1)

Further parameter →  11, table "Parameter"•

Minimum value lower switching threshold = 0 ; negative values are notadmissible.

•Maximum value lower switching threshold = F.S.R. – 1 % hysteresis.

Zero_Adjust_Value contains the zero pressure offset value required for zeroing(writable and readable).
•Automatic zero_adjust function via key or command (→ table "Variables forbytes No. 2 and 3 (special services)").

•Base-Pressure-Adjust for adjusting a defined zero offset, e.g. if the required
final pressure as indicated in the operating manual is not reached.

The Zero_Adjust_Value consists of the high and low byte and has to be convertedwith the "Pressure value" formula (→  4).
Zero_Adjust_Value =Parameter1)

Zero_Adjust_Value1)

Remaining_Zero10<data_value> × ab× F.S.R._Mantisse × 10(F.S.R._Exp)

Description
Zero pressure offset in the selected pressure unit(→  11, table "Parameter").

Further parameter →  11, table "Parameter"

Maximal remaining offset value. The Zero_Adjust can only be executed within thisvalue.

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RS232C.cp

DC Output Level

The "DC Output Level" variable is used for assigning a defined offset level to theanalog output signal, e.g. for setting a certain zero offset signal level.
A "DC Output Level" >0 reduces the output range of the measurement
range 0 … 10 V by the selected offset value (F.S.R. - DC output level).
The "DC Output Level" parameter (16-Bit) consists of the high and low byte.

DC Output Level =Parameter 1)
DC Output Level1)

Software version

Parameter<data_value>

Parameter<data_value>ab

Description
DC-Output-Signal in the selected pressure unit(→  11, table "Parameter").

<data_value>
20

F.S.R._Mantisse
F.S.R._Exptira49e1-b(2016-01)

RS232C.cp

e.g. <data_value> = 20 ≙ V1.0

Description
1 byte value (8 bit), data value in decimal format.

Description
Zero offset measurement data, consisting of "low and highbyte" (16 bit value), data value in decimal format.
Conversion factor for pressure units other than "Torr"
Torr:
a = 1.00
mbar:
a = 1.3332
Pa:
a = 133.32
Factor for resolution
Page No. 1)

1)

× F.S.R._Mantisse × 10(F.S.R._Exp)

Further parameter →  11, table "Parameter"

Software version =Parameter<data_value> × abb

Output signal

23200010.24 V
33200010.24 V43276710.00 V
F.S.R. factor according to the "Sensor type" variable, which
has to be read separately (→ "Read command").
F.S.R. exponent according to "Sensor type" variable, which
has to be read separately (→ "Read command").

→  3, tabel "Structure of send string", byte no. 1

11

Original: German tira49d1-b (2016-01)

t i r a49e1- b

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