KEKB Power Supply Interface Controller Module
A. Akiyama, T. Nakamura, M. Yoshida, T. Kubo, N. Yamamoto and T. Katoh
KEK, High Energy Accelerator Research Organization
1-1 Oho, Tsukuba 305, Japan
Abstract
There are more than 2,500 magnet power supplies for
KEKB storage rings. It was a very important problem tosolve the problem how to control such a large number ofpower supplies distributed around the ring. Almost all themagnets are powered by independent power supplies.
The cost of interfaces is also a large problem. Afterdiscussions, we decided to develop an interface controller
module that will be mounted in the power supply
controller or power supply itself. It has a 16-bit
microprocessor, ARCnet interface, trigger pulse input
interface, and general-purpose parallel interface to thepower supply. The microprocessor receives commands
from the control system via ARCnet, analyzes them andsends signals to the power supply. It does not have DAC
or ADC for simplicity. DAC is located in the power
supply controller or power supply itself. And the output
current is monitored by analog scanning sub-system. We
have also developed an ARCnet driver module on VMEbus with four channels of ARCnet interface. On eachARCnet segment, up to twenty power supply interface
modules are connected. Modules are now being tested inthe QCS magnet power supply system.

1 Introduction
KEKB accelerator is composed of two storage rings, e.g.
an 8GeV electron storage ring and a 3.5GeV positronstorage rings. Both are now being cnstructed in the sametunnel of TRISTAN, a 33GeV electron-positron colliding
accelerator which was shut down and removed from thetunnel. KEKB storage rings are designed for producing B
mesons in the asymmetric way. The parameters of thestorage rings should be adjusted by the operators ormachine physisists through the control system[1]. For
these purposes, almost all magnets are powered byindependent power supplies. Therefore, there are morethan 2,500 magnet power supplies in various categories.
There are small number of very high current power
supplies, several hundreds of medium current ones, andmore than 1,600 steering magnet ones. There are unipolar
power supplies and bipolar power supplies.
To connect those power supplies with the control
computer system is another problem. If you connect thepower supply by using parallel interface, more than 30
signal lines are needed to get status signals, to control andto set DAC value signals. It gives the total of 100,000
signal lines around the storage rings. In order to reduce
the number of lines and the cost of wire handling at thesame time, we decided to connect the power supplies byserial field buses. There were candidates of field busessuch as ARCnet, CANbus, Profibus, and so on. In Japan,
not only KEK but also companies had not enoughexperiences on CANbus, Profibus, and new ones. But
ARCnet had been used widely and we chose ARCnet as
the field bus.
It is very convenient for us if there were power supplies
that can be connected to ARCnet with the software
protocol which we define. To satisfy this condition, atfirst, we asked the power supply manufacturers if they
could inplement such control interface inside their power
supllies but the answers were negative. Then, we decided
to develop a power supply interface controller module inEuro-Card format which can be plugged into the power
supply and link it to the control system.

2 Requirements for the module
As described above there are several types of power
supplies. There are unipolar and bipolar power supplies,
new and modified old ones, 12 bits and 16 bits inaccuracy, required specifications for such power supplies
are widely distributed. We decided to design the software
installed on the Power Supply Interface Controller
Module(PSICM) recognizes which kind of power supply
is connected. In other words, each power supply musthave its unique type and serial number data in itself. The
PSICM can be used for other purposes by changing
software written in EPROM.
The magnet power supplies will be operated in threemodes; direct, constant slewing rate, and wave-generator
modes. In all modes, the DAC set value is sent to thepower supply by either software commands or hardware
start pulse signal.
2.1 The direct output modeThis is the most fundamental mode for diagnostics, inwhich the magnet current is set directly to a certain value.
2.2 The constant slewing rate mode
Usually the magnet current is set by using this mode.
The parameters are target current value, time to be usedand delay time before starting. In this mode, when thecommand is accepted, the microcontroller calculates thechange during the unit time period(e.g. 1ms) and magnet
current will be incremented every unit time after the given
delay time. The sequence can be triggered either bysoftware start command or hardware start signal.

2.3 The wave-generator mode
Sometimes it is required to change magnet currents ofdifferent types synchronously and proportionally or in thecalculated manners. In this case series of magnet currents
for each magnet are calculated by the application programand put into an array which will be sent to PSICM via
ARCnet. After PSICM receives all the data, a software
start command or hardware start signal will be sent to themodeule and the module passes the output value to thepower supply every pre-determined interval till the data
runs out.
In the extreme case it is requested to the control system
to be able to adjust magnet currents of 800 steering
magnets in 400ms synchronized with each other for
keeping the beam stable in the storage ring. Thefundamental hardware specifications are listed in Table 1.

The PSICM itself was designed as a general-purpose
module. Physically, it has the shape of 100mm x 160mm
Euro-Card format with a DIN 64-pin connector as shownin Fig. 1. Intelligence is provided by a 20MHz 16-bit
microcontroller chip of 80186 type. Communication withthe host VME computer is done through the ARCnet
interface controller chip and a driver module. Interface tothe power supply is done through a 64-pin DIN 41612
type-C connector and DC power consumed by the moduleis also supplied through this connector.
The ARCnet cable is connected through two RJ-45
STP(Shielded Twisted-Pair) connectors. One is for theupstream and the other is for the downstream. The circuit
diagram is shown in Fig. 2.

Table 1. Table of the basic parameters of PSICM.
Physical size:
Network connectors:
Signal connector:
Microcontroller:
Clock frequency
Data memory:
Program memory:
Power required:

100mm x 160mm x 6 HP
2 x RJ45 STP connectors
DIN 64-pin connector
AM186 16-bit Microcontroller
20MHz
256kB SRAM(128kB x 2)
256kB EPROM (128kB x 2)
5V 0.4A

Communication interface
Network:
2.5Mbps ARCnet Backplane mode
Nr. of nodes:
20
Cable:
Category 5, STP cableMax. length:~ 150mPower supply interface
Dedicated lines
CBON (out)1 bit (Momentary)
CBOFF (out)1 bit (Momentary)
PWRON (out)1 bit (Momentary)
PWROFF (out)1 bit (Momentary)
POL+ (out)1 bit (Momentary)
POL– (out)1 bit (Momentary)
DAC strobe (out)1 bit (Momentary)
RESET (out)1 bit (Momentary)
Attention (in)1 bit (Momentary)
General purpose I/O lines
Register address (out) 4 bits
Read strobe (out)1 bit (Momentary)
Write strobe (out)1 bit (Momentary)
Data input (in)16 bits
Data output (out)16 bits
3 Hardware configuration

Figure 1.
ModuleA Power Supply Interface Controller

3.1 Microcontroller
A 16-bit microcontroller 80186 type is used in thePSICM to control a power supply and to handle ARCnet
communication with the VME control computer in theKEKB control system. Two 128k bytes static RAMs areused for data memory storage. The programs are stored ina pair of EPROMs. Each EPROM has a capacity of 128kbytes. The clock frequency of the microcontroller is10MHz. The chip provides a watch-dog timer facility forrecovery of the system from the dead-lock problem.
3.2 ARCnet Interface
The module is connected to the host VME computer via
single shielded twisted-pair cable with two conductor
pairs, one for the ARCnet and the other for the start signal
for synchronous ramping. The back-plane mode isadopted in KEKB control system and up to twenty PSICM
can be connected in one segment. The ARCnet is a tokenbus network and PSICMs are logically connected to a bus
line but shielded twisted-pair cables are used to connect
PSICMs in a daisy-chain manner.

Microcontroller

TLP121

INT2

INT1AM186EM
20MHz

OpticalCoupler

RJ-45

ATTEN
OUT01620MHz

LATCH

D0~D15COM20020

RJ-45

HYC2485

MediaInterface

A0~A158ADDRESSDECODING
LOGIC

OUT15IN016LINE
RECVR.

RAM 2kB

IN15

ARCnet
EPROM
256kB

RESET

10LATCHSRAM
256kB

DIN 41612 Type-C 64-pin Connector

SYNC

RD

D0~D155LATCH

A0A4Fig. 2. Circuit Diagram of Power Supply Interface Controller Module

4 Software
The magnet power supply has its unique data such aspower supply type identification code, the serial number,and the calibration constants in the NVRAM in the power
supply itself. These data are read by the PSICM at its
initial start-up phase.
The main routine of the program waits for the ARCnet
interrupts, attention signal from the power supply, startsignal input or timer interrupts. The ARCnet interrupt
shows the arrival of commands from the VME computer
and the command is analyzed and executed. The
commands includes the three major operationg modes ofthe power supply, e.g. direct mode, constant slewing ratemode, and the wave-generator mode.
Attention signal from the power supply shows changes instatus of the power supply and the program checks thestatus and send them up to VME computer if it must bereported. The start signal interrupt triggers the output
to DAC and the program continues to output periodicallyby the tick of the internal timer. The timer interrupts areused to get constant period of 1ms and 10ms.

If the power supply has a circuit breaker in the power
input circuit, it can be switched on/of by sending
CBON/CBOFF commands.
The output current isswitched on/off by sending PWRON/PWROFFcommands. The polarity of the output current can bechanged by sending POL+/POL- commands. Alarm status
can be reset by the RESET command when the power
suplly error occurs.
The PSICM routinely watches the status of the power
supply and sends the alarm message to the host VME
computer if the status change is detected and it must be
noticed. The output current of the power supply will bemonitored by the VME computer using a scanning analog
volt-meter.

5 QCS Magnet power supplies
KEKB storage rings are under construction and atpresent, we have only a part of magnet power supplies.
We have installed PSICMs in the QCS(Quadraplemagnets for the Colliding points using Super-conducting)and correction magnet power supplies as shown in Fig. 3.
In the figure, you can see PSICMs are installed in themagnet power supplies. QCS magnets are being tested
now with PSICM in themselves. The steering magnet
power supplies are now manufactured by a company.

6 Conclusion
The PSICM was developed for the KEKB magnet power
supplies and it reduces number of cables and number ofconnections dramatically. The PSICM itself is designed
general purpose module in standard format so that it canbe used for various purposes by the modification of thesoftware on the module.

7 Acknowledgments
We wish to express our thanks to the members of KEKB
controls group and KEKB magnet group for theircooperations. We also thank Prof. Shin’ichi Kurokawa
for encouraging the development of PSICM.

8 Reference
Fig. 3. PSICMs installed in QCS correction magnet power
supplies.

[1] “Present Status of the KEKB Control System”, T.
Katoh, et al., ICALEPCS’97, this conference.