Mitsubishi A Series User manual

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REVISIONS
*The manual number is given on the bottom left of the back cover.
Print Date
Jan.,
1992
*Manual Number
IB (NA) 66360-A
Revision
~
First edition
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INTRODUCTION
Thank you for choosingthe Mitsubishi MELSEC-ASeries of General Purpose Programmable
Controllers. Please read this manual carefully
so that the equipment is used to its optimum.
A copy of this manual should be forwardedto the end User.
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CONTENTS
1. GENERAL DESCRIPTION . . . . . . . . . .. . . .. . . . . . .. . . . . . . . . .. . .. .. . . . . 1 - 1 1 - 10
1.1 Features .. .. .... ........................ . .... . ...... .............. .... 1-4
1.1.1 Control operations in data communications . . .. . . ... .. . . . . . ... . . . ... .. 1 - 4
1.1.2
System configuration and the number of stations when a computer
link system
is constructed . .. . .. . . .. . . .. . ... ... . .. . . . . . , .. , . . , . . .... 1 - 7
1.1.3
Link with a computer through datalink systems ... . .. . . . . .. . . . . .. . . .... 1 - 9
1.1.4
Modeswitchingfunction . . . . . . . ... ... . . .... . . .. . . . .. . .. . . . .. . . . ,, . 1 - 10
1.1.5
Transmission control function .. . . . . . .. . . ..... .... . .. . . , . . .. . . . . .. , 1 - 10
2 SYSTEM CONFIGURATIONS .. . .. . . . . .. .. . . .... ... . . . . .. . . . . . . . . .2 - 1 - 2 - 21
21 Overall Configurations . ... . . . . . .. .. . . . . . . .. . . . .... .. . .. . . . . . ..... . . .. . , .. 2- 1
2.3 System Configurations and Available Functions .. ... . .. .. . . . . . . . ..... , . .. . , .. 2 - 4
23.1 1 : 1 ratio of an external device (computer) to a PCCPU . . . . .... . . . .. .. . . 2 - 4
23.2
1 : n ratio of an external deviceto PC CPUs . .. . . . . . . . . .. . .. . . .. ... . , . . 2- 7
23.3 2:
1 ratioofextemaldevicestoaPCCPU ......... .. .............. ,. 2-10
2.3.4
2:nratioofextemaldevitoPCCPUs ............................ 2-13
2.3.5
m:nratioofextemaldevicestoPCCPUs ... ........................ 2-16
23.6
Links with an external device (such as a computer)
through datalink systems . . . . . .. ... ... . .. . . . ...... . . . .. , .. , . . , .. , . 2 - 19
2.2
, ApplicableSyst~~~~ ..................................................... 2-2
3.1 GeneralSpeCificati . . . .. . . .. . . . .. . . .. .. .. . . . . . . . . .. . .. .... ... . . .... . 3-1
3.2
Perf~nnan~eSpeCificatiOns . . . .. . .. ... .. . .. . . .. . ... . . . .... .... . . . . . . . , .. ,, 3-2
3.2.1
Transmbsionspecifications.. . . . . .. .. ... . . . .. . . .. ... . . .. .... . . . . . . . . 3-2
3.2.3
RS422 terminalMock specifiions . . .. . . . . . . . .. , . . . . . . . .. . .. . . . , . , . 3 - 5
3.3 Data Communications Functions . . . . . . . . . . .. ... ... . . . . . ... ,, . . .. , . ... . , , , . , 3 - 6
3.3.1
Functions available using dedicated protocots and commands . . .. . . , ... , 3 - 6
3.3.2
Functions available in the no-protocol mode . . .... ..... . , . . . . , . .. . , .. , 3 - 13
3.3.3
Functions available in the bidirectional mode . . . .. . , . ,, . ,, .. , .. . ... . , . 3 - 14
3.3.4
Transmission error data read function . . . .. .. ... .... , .. . . ,, .. , . . . .. . . 3 - 15
3.4
Mode Switching Function During A171C24 Operations . . . . . . . ,,,,, .. , .. , ... . . , 3 - 16
3.4.1
Precautions when mode switching . . . . . . . . .. . . ... . , . . . , . . ... . . . . . , . 3 - 16
3.4.2
Procedure for switching the mode from an external device .. . . . . . . . . . . . . 3 - 20
3.4.3 Procedure for switching the mode from a PC CPU . . .. . ... , . , .. , .. , . , . . 3 - 22
3.5 Data Communications Transmission Control Function . . . . . . .... ... ... . , . . . , .. 3 - 24
3.5.1
Precautions when controlling transmission . .. . . .. . . ... . ... . . .. . . . .. .. 3 - 24
3.5.2
DTR /DSR (EWDR) control. . . . . . . . . . . .. . . . .. . . , . . . .... . . . .. , .. , . . . . 3 - 28
3.5.3
DCl/DC3transmission control . . . ..... . .. ... .. .. . . .. .... . . .. ... . , . . 3 - 30
3.5.4 DCl/DC3 receive control . . ... ... . . .. . . . . . . .. . .. . . . . .. . .... .. .. ... , 3 - 31
3.5.5
DC2DC4sendcontrol ............................................ 3-32
3.2.2
RS-232CCOnnectOrspecificati ... .. ... . . . ... . .. . .. . .. .. . . . . . . . . . . 3-3
3.2.4 RS422caMe~pecifications.. . . . . . . . . . ... .. . . .. . . .. ... .. . . ... .. , . ,, 3-5
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3.5.6 DC2/DC4receive contrd .......................................... 3-32
3.6
I/OSignalsListfOfCPU .................................................. 3-33
3.7
BufferMemoryApplications and Allocation .................................. 3-36
4 . SElllNGSANDPROCEDURES BEFORE OPERATION .................. 4 . 1 . 4 . 21
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Settings and Procedures More Operah'on .................................. 4 . 1
Nomenclature .......................................................... 4 . 2
4.2.1
Nomenclature .................................................... 4-2
4.2.2
LED signals and displays .......................................... 4-3
Settings ............................................................... 4-5
4.3.2
Setting of transmission specifiiions. main channels.
andterminalresistance ............................................ 4-6
4.3.3
Stationnumbersetting ............................................ 4-9
Loadingandlnstallation ................................................. 4-10
4.4.1
Handlinginstructions ............................................ 4-10
4.4.2
Installationenvironment .......................................... 4-10
Externalwiring ........................................................ 4-11
4.5.1
Precautionsduringwiring ......................................... 4-11
4.5.2
Connectingthe RS-232C connectors ............................... 4-11
4.5.3
Connectingthe RS422 connectors ................................. 4-13
4.3.1 Setting the dedicated protocol. no-protocol mode. or bidirectional mode ... 4 - 5
4.5.4 Connecting a muitidrop link and setting modes and terminal resistance ... 4 - 14
Self-loopback Test ..................................................... 4-17
4.6.1 Proceduretocarryouttheself-loopbacktest ......................... 4-17
4.6.2
Setf-loopback test operations ...................................... 4-19
InspectionandMaintenance ............................................. 4-21
LWpbaCkTest ........................................................ 4-20
5 . HALF-DUPLEX COMMUNICATIONS USING THE RS-23X INTERFACE ...... 5 . 1 . 5 . 9
5.1 System ConfigurationsandFunctions ...................................... 5 . 1
5.2 Buffer Memory Settings .................................................. 5-2
5.3 Wiring ................................................................ 5-3
5.4 ON/OFF Timing of the CD and RS Signals of the AJ71C24 ..................... 5-4
5.4.1
Datatransmissiontiming from an external device ...................... 5-5
5.4.2 Datatransmissiontiming from an A171C24 ........................... 5-7
6 . DATA COMMUNICATIONSUSING AN M : NMULTIDROPLINK ........... 6 . 1 6 . 11
6.1 KeyPoints .............................................................. 6-1
6.2
ConditionsforComputerInterlock .......................................... 6-2
6.2.1
Computer station number allocation ................................... 6-2
6.2.2
Maximum data communications time per computer ...................... 6-3
6.2.3
Command and message format for data communications
amongcomputers ................................................. 6-4
6.3
ProcedureforDataCommunications with a PCCPU ........................... 6-5
6.3.1
Communicationsbetween each computerand PC CPUs ................. 6-5
6.3.2
Data communications with PCCPUs by setting a master station and
slavestations ..................................................... 6-8
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7 . INITIAL SETnNG OF TRANSMISSION CONTROL DATA TO
BUFFER MEMORY ............................................... 7 . 1 . 7 . 21
7.1 setting Rs-232C CDTerminal Check Enable/Diile ........................... 7 -2
7.2 Setting the Transmission Method for RS-232C ................................. 7-3
using "a alfduplextransm'wsion ....................................... 7-4
7.2.1
Setti prioritv of transmission tothe A171 C24
7.2.2 Setting non-priority of transmission tothe A171C24
withthehdfdwttansmission ..................................... 7-5
7.3
ReadingTransmission Error Data ........................................... 7-7
7.3.1
Readingthe error LED display status .................................. 7-7
7.3.2
Turning OFF error LEDs ............................................. 7 -8
7.4 Settings in the No-Pratocol Mode ........................................... 7 -9
7.4.1 Setting the m>-protocd mode receive-completed code
(for receive with
VariaMe-length data) .................................. 7 -9
7.4.2 Specifying no-protocol receive completion data length (fixed length) ....... 7 - 10
7.4.3 Settingawordorbyteunitintheno-protocolmode ..................... 7-11
7.4.4
Setting a buffer memory area for no-protocol send ...................... 7 - 12
7.4.5
Setting a Mermemory areafor no-protocol receive .................... 7- 13
7.5
Settingsin the Bidirectional Mode .......................................... 7 - 14
7.6
ModeSwitchSetting ..................................................... 7-17
7.6.1
Readinginthemodesettingstate ................................... 7-17
7.6.2
Mode switchingdesignation ....................................... -7 - 18
7.7
TransmissionControlSetting ............................................. -7 - 20
7.7.1 How to set transmission control ..................................... 7 -. 20
7.7.2 Settingsfor changing theaddresses of DC1 to Dc4 codss ............... 7 - 21
8 . COMMUNICATIONSUSINGDEDICATEDPROTOCOLS ................ 8 . 1 . 8 . 11 2
8.1 Data Flow in Communicationswith Dediied Protocols ....................... 8 . 1
8.2 ProgrammingHints ...................................................... 8-2
8.21
To write data to the special use area in buffer memory .................. 8 -2
8.22 PC CPU operationduringdatacommunications ....................... 8 -3
8.23
Precautionsduringdatacommunications ............................. 8 -4
8.3
Basics of DedicatedProtocolControlProcedures ............................ 8 -5
8.4 BasicFormats of Dedicated Protocd ....................................... 8 -6
8.4.2
Control format2 .................................................. 8-8
8.4.3 Controlformat3 .................................................. 8-9
8.4.4 Control format4 ................................................. 8- 10
8.4.5 Setting protocol data ............................................. 8- 11
8.5 Transmission Sequence TimingCharts and Communications Time ............. 8 - 16
8.6 Character Area DataTransmission ........................................ 8 - 1 9
8.7 DeviceMemory Reamrite .............................................. 8 - 22
8.7.1 Commandsanddeviceranges .................................... 8-22
8.7.2 Batch read in units of bits ......................................... 8 - 28
8.7.3
Batch read in units of words ....................................... 8 - 30
8.7.4 Batchwrite in units of bits ......................................... 8 - 34
8.4.1 COWOIfOrmatl .................................................. 8-7
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8.7.5 Batchwriteinunitsofwords ....................................... 8-36
8.7.6
Testingdevicememoryinunitsofbit(randomwrite) ................... 8-40
8.7.8
Monitoringdevicememory ........................................ 8 - 44
8.8 ExtensionFileRegister Read and Write .................................... 8 - 53
8.8.1 ACPUcommon commands and addresses .......................... 8 - 53
8.8.2 AnACPU dedicated commands and device numbers .................. 8 - 55
8.8.3 Precautions during extension file register read/write ................... 8 - 58
8.8.4 Batch read of the extension file register (ACPU common command) ...... 8 - 59
8.7.7 Testingdevicememoryinunitsdwords(randomwrite) ................ 8-42
8.8.5
Batch write of the extension file register (ACPU common command) ..... 8 - 60
8.8.6 Direct readof the extension file register (AnACPU dedicated command) . . 8 - 61
8.8.7
Direct writeto the extension file register (AnACPU dedicated command) . . 8 - 62
8.8.8 Testing (random write) the extension file register
(ACPU
common command) ....................................... 8 - 63
8.8.9 Monitoring the extension file register ................................ 8 - 64
8.9 Buff& Memory ReadandWrite ........................................... 8 - 67
8.9.1
Commandsandbuffer memory .................................... 8 - 67
8.9.2
Reading data from buffer memocy (ACPUcommoncommand) .......... 8 - 68
8.9.3 Writing data to buffer memory (ACPUcommoncommand) ............. 8 - 69
8.1
0 Special Function Module Buffer Memory Read and Write ..................... 8 - 70
8.1 0.1
Commandsanddesignation ...................................... 8 - 70
8.10.2
Special function module numbers usingcontrd protocols .............. 8 - 72
8.10.3
Reading data from the special-function module buffer memory
(ACPUcommoncommand)
....................................... 8 - 74
8.10.4
Writing datatothe special function module buffer memory
(ACPUcommoncommand) ....................................... 8 - 75
8.1
1 Remate Run/Stop of PCCPU and Reading PC CPU Model Name .............. 8 - 76
8.11.1
Commands ..................................................... 8-76
8.1 1.2
RemoteRUN/STOP .............................................. 8 - 77
8.1 1.3 ReadingPCCPU model name ..................................... 8 - 79
8.1 2.1 Precautions during program reaWrite .............................. 8 - 80
8.12 ProgramReadWrite .................................................... 8-80
8.12.2
Program read/write control procedures .............................. 8 - 81
8.12.3
Parametermemoryread/write ..................................... 8 - 83
8.1 2.4 Sequence program read/write ..................................... 8 - 87
8.1 2.5
Microcomputer program read/write ................................. 8 - 93
8.1 2.6 Comment memroy read/write ...................................... I 8 - 97
8.12.7
Extensioncommentmemoryread/write ............................ 8 - lo0
8.13
GlobalFunction ...................................................... 8-103
8.1 3.2
Setting the global function (ACPU common command) ............... 8 - 104
8.14
Ondemand Function .................................................. 8 - 105
8.1 4.1
Ondemandhandshake signal and buffer memory ................... 8 - 105
8.14.2
Ondemandfunction control procedure ............................ 8 - 106
8.1 4.3
On-demand function designation .................................. 8 - 109
8.15
LoopbackTest ....................................................... 8-112
8.13.1
Commandsandcomrol ......................................... 8-103
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9. COMMUNICATIONS WlTH A COMPUTER IN THE NO-PROTOCOL MODE . .9 - 1 - 9 - 18
9.1
BasicsofthebPrdocdMode ........................................... 9-1
9.2
Handshakel/OSinals .................................................. 9-2
9.3
ProgrammingHints ...................................................... 9-3
9.3.2
Precautions during data communications ............................. .9 - 4
9.4
Basic ProgramtoReadmriteBufferMemory ................................. 9 - 6
9.3.1
Towritedatatothespecialuseareainbuffermemory .................... 9-3
9.5
ReceivingDataintheN~ocolMode(ExtemalDevice-.AJ71C24) ........... 9-9
9.6
SendingDataintheNo-PratocdMode(A171C24~ExtwnalDevice) ........... 9-15
10.
COMMUNICATIONSINTHEBIDIRECTIONALMODE ................. 10 - 1 10 - 26
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
BidirectionalModeBasics ............................................... 10-2
Handshake Si- and Buffer Memory .................................... 10 - 4
ProgrammingHints ...................................................... 10-8
10.3.1
System configuration and commuflications mode for bidirectional
modecommunications
........................................... 10-8
10.3.3
Precautions during data communications ........................... 10 - 10
Bidirectiod Control Procedure Basics ................................... 10- 12
BidirectionalCommunicatii Basics ..................................... 10 - 13
10.3.2
Towritedatatoaspecialappkatiiareainbuffermemory ........... 10-9
10.5.1 COntrd~dOCQk
............................................... 10-13
Processing an A171 C24 for Simuttarmus Send in FulCDuplex Mode .......... 10 - 17
Receiving Data in the Bidirectional Mode (Computer + A171 C24) ............. 10 - 20
Transmitting Data in the Bidirectional Mode (A171 C24 -. Computer) ........... 10 - 23
10.5.2 Messageformat ................................................ 10-14
Basic Programto ReadMlrite Buffer Memory ............................... 10- 18
11. TROUBLESHOOTING ........................................... 11-1 -11-9
11.1 NAKErrorCodeswithDedicatedProtocds ................................. 11 -1
11.2 BidirectionalModeErrorCodes .......................................... 11 -3
11.3
TrouMeshoatingOFF ................................................... 11-4
11.3.1
TrouMeshootingflowchart ........................................ 11-4
11.3.3
Whentheneutralstatedoesnotchangeordataisnatreceived ......... 11 -6
11.3.4 Whenthe2-C/N(LEDNo.16)or4-CM(LEDNo.20)istumedON ....... 11-7
11.3.2
Whenthe'RUN'LEDistumedOFF ................................ 11-5
11.3.5 Whencommunicatiisometimesfails ............................. 11 -8
11.3.6 Whenundecodeddataistransmitted ............................... 11 -9
APPENDICES .................................................. APP-1 - APP-27
APPENDIX
1 Precautions Concerning Compatibility and the Use of
Existing Programs Prepared forthe AJ71C24 Computer Link Module ...... APP - 1
1.1
Compatibility ......................................................... APP-1
1.2 Precautions when Using Existing Programs ............................... APP - 1
1.3 Function Comparison ................................................. APP-2
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APPENDIX 2 Precarrtkns concerning Compatibility and the Use d Existing
Programs Prepared forthe A171C24S3 Computer Link Module .......... APP - 4
2.1Compatibility
......................................................... APP-4
2.2 PrecautionsWhenUsing
Existing Programs ............................... APP - 4
2.3 FunctionComparison
.................................................. APP-5
APPENDIX 3 Precautions Concerning
Compatibility and the Use of Existing
Programs Prepared for the AJ71C24S6 Computer Link Module .......... APP - 6
3.1 Compatibility ......................................................... APP - 6
3.2 Precautions When Using Existing Programs ............................... APP - 6
3.3 FunctionComp'son .................................................. APP - 6
APPENDIX 4 ASCIICode Table ................................................ APP - 7
APPENDIX
5 Communications Time between aPCCPU and an A171C24 ............. APP - 8
APPENDIX
6 Precautions During Communications When Using -22 Interface ...... APP - 11
APPENDIX 7
Sped Function ModuleBufferMemoryAddresses ................... APP - 13
APPENDIX 8 SequenceProgram Example Showing How to Output
WordDevice Data
to the Printer in the No-Protocol Mode ............... APP - 18
8.1
WhenOtherThanAnACPUisUsed ..................................... APP-18
8.2When
the AnACPU is Used ............................................ APP -20
APPENDIX 9 Example of a SequenceProgram for DataCommunications
in the Bidirectional Mode .......................................... APP - 21
APPENDIX 10ExternalView ................................................... APP - 24
APPENDIX 1 1 A171 C24
Setting Record Form ..................................... APP - 25
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1. GENERAL DESCRIPTION MELSEC-A
1. GENERAL DESCRIPTION
This User's Manual describes the specifications, handling andtransmission
control protocolsof the
AJ71C24-S8 computer link module.
The
AJ71C24-58 has one RS-232C port and one RS-422 port. It is the
interface between a
PC CPU and an external device (such as a computer or
printer) or to the
CPU of another PC station.
Dedicated transmission protocols
1 to 4 are used as transmission control
procedures on the
AJ71C24-S8 and a no-protocol mode anda bidirectional
mode are also available. The user can select and set these independently
for the
RS-232C and RS-422 ports.
Whenusing
a dedicatedtransmissionprotocolortheno-protocol
mode/bidirectional mode, data
is transmittedusing the codes as shown
below.
~
Autome communications
earths sequence prqm
FlS232Cor Rs-422 cableComputer
PC ENDpmemsing.
BIN code
AJ71
'
CPU ASCIIcode (ASCIIcode)
C24
. .
Read
Write
Transmitted data
\
Trammitwd.ta
\
\\
Transmitteddata
- ~AnlC24mmeftsdatabetween -
\
(1234~) BIN code and
ASCII code.)
Fig. 1.1 Data Transmissionwith the Dedicated Protocol
r
Rs232C or -22 cable
Sequence program
CPU
mew'
TOFROM inetwctions
PC
BUnW
C24
Oon to FFH
AJ71
. .
External device
(such
as a computer, printer)
Oac to FFH
Transmit
Receive
T
I
(Data is transmitled in unchanged code through the buffer memory.)
Fig. 1.2. DataTransmissioninthe No-Protocol Mode/Bldirectional Mode
I
1-1
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1. GENERAL DESCRIPTION MELSEC-A
Compared with the AJ71 C24-S3and AJ71 C24-S6computer link modules,
the AJ71C24-S8 supports the followingsix additional functions:
[(l) to (6) are the additional functions when compared with the AJ71 C24-S3]
(1) Commands dedicated for use with the A2ACPU(Sl) and A3ACPU:
All memory devices of the A2ACPU(S1) and A3ACPU (the AnACPU
in
this manual) are accessible usingthese dedicated commands.
(2) Data transmission
in the bidirectional mode:
This feature allows the AJ71 C24-S8to interface
1 :l data communica-
tions usingthe ACK code between a PC CPU and a computer.
When data is transmittedfrom the AJ71 C24-S8to a computer, a control
code
ENQ, the data length code, and a check sum are added respec-
tively to thebeginning, the middle, and the end
of the send message.
(The check sum is optional.)
When the AJ71C24-S8 receives data from a computer,
it transmits a
control codeACWNAK back to thecomputer. This indicatesthe result
of the receive (normal/abnormal).
The AJ71C24-S8thus adds the
ENQ code, data length, and check sum
and checks
the reception of the response message at the data trans-
mission.
It checks the received data andsends the response message
after
it received data.
The length
of a data communications sequence program can beshor-
tened by using the bidirectionalmode.
(3) The communications mode using
the RS-232C interface can be set to
either full-duplex or half-duplex:
ThecommunicationsmodeusingtheRS-232Cinterface of the
AJ71C24-S8 can beswitched either tofull-duplex or half-duplex accord-
ing to thespecifications of the peripheral device.
(4) Multidrop link
with more than one computer is possible:
More than one computer canbeputintoamultidroplinkwiththe
AJ71 C24-S8.
The PCCPU modules
in the multidrop link can be accessed from the
computers for read/write of device data and sequence programs.
1-2
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1. GENERAL DESCRIPTION
, L. , MELSEC-A
1(5) and (6) are the additional functions when compared with theAJ71C24=S6]
(5) Mode switching function when the AJ71C2448 operates
TheAJ71C24-S8'sRS-232C/RS-422interface canbeswitched between
the following modes after a start-up:
N+pratocol mode . . Bidirectional mode
(6) Transmission control function using DCl/DC3 and DC2/DC4
Datacommunications betweentheAJ71 C24and anexternal device can
be controlledby using theDCl/DC3 and DC2/DC4 codes.
DCl/DC3 sendcontrol, DCl/DC3 receive control: Enables or disables
data send andreceive.
DC2/DC4 send control, DC2/DC4 receive control:Controlsthe valid
range of sendheceive data.
tf any exirting program are ured with the AJ71C24-S8, reo Appendix 1.2.3 for interchan-
geability between the AJ71
C24-S8 and thefollowing devicer.
0 AJ71C24 computer link modules
0 AJ71 C2CS3 computer link modules
0 AJ71C24-S6 computer link moduler
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1. GENERAL DESCRIPTION MELSEC-A
1.1 Features
The features of the AJ71C24-S8 computer link module (hereafter called the
AJ71C24
in this manual) are given below.
1.1.1 Control operations In data communications
Datatransmission operations between an AJ71 C24and external devices (e,
g., computers) can be controlled using either the dedicated protocols
(*1)
or in the no-protocol/bidirectional mode. These control operations can be
selected individually with theRS-232C and
RS-422 ports of an AJ71C24.
(1) Communications usingthededicatedprotocols
Communications at the request of the computer
Data communications is always initiated
by the computer.
Designated data istransmitted accordingto the requestcommand
transmitted from a computer to an AJ71C24.
It isnot necessary tocreateandchangespecialsequence
programs in order to use an AJ71C24.
Read and write possible to andfrom all PC CPU devices
Data can be read from all
PC CPU devices. This permits obser-
vation and monitoringof all operations, as well
as the collection
and analysis of data. Datacan bewritten to all PC CPU devices.
This permits production control and production directivesto be
carried out.
An AJ71C24can uploadand download programsfrom aPC CPU.
PC CPU programs (main sequence and subsequence control
programs and microcomputer programs), parameter dataand
comment data are read by the computer and stored. When
required they can be written to
the PCCPU to changethe
program.
Remote RUN and STOP control of the PC CPU
The PCCPU can be remote-controlled by means
of RUN and
STOP instructions from the computer.
When multiple computers and PCCPU modules are connected
to a link with an AJ71C24 module, the input (X) signals of the
CPUs in the link can be turned
ON/OFF using any computer in
the link. This function can immediately stop or simultaneously
start all
CPUs in the link.
(This function is called the globalfunction of the AJ71C24.)
Communications at the request of the
PC CPU
The
PC CPU transmits the data send request.
When the emergency data needs to be transmitted from aPC CPU
toa computer, the
PC CPU transmits asend request to theAJ71C24
to make the computer execute an interrupt processing.
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(Thisis theon-demandfunction of the AJ71 C24. It is availabte
only when one computer is connected to one PC CPU.)
* 1 : The dedicated protocolsconsist of four different protocols.
The term 'dedicated protocols' used in this manual is the col-
lective term for these protocols.
(2) Communications in the no-protocoVbidirectiona1 modes
Either the no-protocolmode or the bidirectional modecan be set.
(a) Communications in the no-protocol mode
1) Data communications can be initiated by a PC CPU
Data communications can be initiated
by a computer or any PC
CPU. Data canbe transmitted from a PCCPU to an external
device by using the
TO instruction in the sequence programto
write data tothe buffer memory.
Data transmitted from an external device can
be read by a PC
CPU using the
FROM instruction in the sequence program.
The following example shows a system with a printer, CRT and
keyboard terminal connected in a
1:1 ratio. Data can be output
from the buffer memory tothe printer or a CRT display using the
TO instruction. Data input from thekeyboardtothe buffer
memory can be read using a
FROM instruction fromthe PC CPU.
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-
TO instruction
(write) (Send) Printer, CRT, computer
PC CPU
FROM iMtruction
AJ71 C24
Computer, keyboard
L
(F-Q
2) Receiving data length canbe set to variable or fixed:
The Length of
the data transmitted from an external device and
received by the PC CPU can be set to variable or fixed.
i) Receiving variable-length data:
Data receive stops when the receive completed code set by
the user is received.
ii) Receiving fixed-length data:
Data receive stops when the fixed length of data set by the
user is received.
Both the receive completed code and thereceive-completion
data length can be freely set by the user.
3) Variable communications memory area
The user memory area can be allocated to suit the purpose and
application of the datatransmission.
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1, GENERAL DESCRIPTION
MELSEC-A
(b) Bidirectional communications
1) Data communications can be initiated by a PC CPU
Data communications can be initiatedby a computer or any PC
CPU. Data canbetransmittedfrom a PCCPU to an external
device by using the TO instruction in the sequence program to
write data to the buffer memory.
The data send operation is completedwhen the response mes-
sage to the sent (received) data is received from the computer.
The result of the send (normal end/error) is stored
in the buffer
memory and can be readout.
The data receivedfrom the computer can beread withthe
FROM
instruction of the sequence program.
(When data is transmitted by an AJ71C24)
TO instructionData send
Xno ON Reapomereceke
PC CPU Computer AJ71 C24
(Send complasd)
FROM instruction
-
(Send result)
2) Data length is set within the sendmessage
Data.length is set within the send message when the data is
transmitted to a device.
The receiving side recognizes the data lengthby the sendmes-
sage.
Data
-pq check
I I I I I
1 T
The send data of the AJ71 C24is processedas follows.
ENQ: ..................... Added to the head.
Data length: ........ The rend data length set inthe buffermemory is transmitted,
Data: ..................... The send data storedin the buffer memoryir transmitted.
Sum check: ......... Computed with the sum checking range ina message.
The data transmittedby a computer and receivedby anAJ71 C24
is processed as follows.
ENQ: ..................... Checked and removed fromthe received data.
Data length: ........ Stored inthe buffer memory as the received data length.
Data: ..................... Stored inthe buffer memory as the received data.
Sum check: ......... Checked and removed fromthe received data.
3) Variable communications memory area
The user memoryarea can be allocatedto suit the purposes and
applications of the datatransmission.
1-6
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1. GENERAL DESCRIPTION MELSEC-A
1 .1.2 System configurrtion and the number of daions when a computer link system is constructed
A computer link system using the dedicated protocol, no-protocolmode, or
bidirectional mode can be constructed by connecting the computer to the
PC CPU in the ratios of 1 :1, l:n, 2:1, 2:n, and m:n. (*1)
When the connection ratio is
l:n or 2:n, up to 32PCCPU stations can be
tied toone link system.
When the connection ratio is m:n,
up to 32 stations of computers and PC
CPU modules can be tied toone link system.
1) When theconnectionratio of the computer tothe PCCPU
module is
1 :n:
This method of linking uses one computer and multiple PC CPU
modules for up
to 32 stations.
Data communications is executed between the computer and
designated PC CPU stations.
This link system is calleda multidrop link system.
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AJ7lc24 (Mi& 0) An1 c24 (stati&2) An1 C24 (strrtio/n 31)
Max. 32 stations (Number of PC CPU stations)
1-7
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1. GENERAL DESCRIPTION
MELSEC-A
2) When theconnectionratioofthecomputer tothe PCCPU
module is m:n:
This method of linking uses more than one computers and mul-
tiple PC CPU modules for up to 32 stations.
Data communications is executed between a computer (which
has acquired theaccess right through thecommunications with
other computers) and designated PC CPU stations.
This system is also called a multidrop link system.
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An1 C24 (Station 0) An1 C24 (Station 1) An1 C24 (Station 2) An1 C24 (Won 24)
Max. 32 stations (Number of PC CPU stations)
1 :The on-demand function andthe data communications in the
bidirectional mode mentioned respectively
in Section 1.1.1
(l)(b) and (2)(b) cannot be used with the multidrop link sys-
tems.
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1, GENERAL DESCRIPTION ,,... , ~
MELSEC-A
1.1.3 Unk with a computer through data link systems
(Twc-tjer system)
M : Masterstation
L :Localaation
R : Remote Vo station
Um : Local /master station
: for the third tier
I :Thir&ierMrtatior
0 autd/mcmm d&a
St.bionthatcan
(Three-tier system)
In a system connected through the following datalink system, if the system
contains a PCCPU connected to a computer via an AJ71C24, data com-
munications is possible between the computer and a PC CPU not equipped
with the AJ71 C24.
However, communicationsisnotpossiblewith AOJ2CPUP23/R23or
AOJ2P25/R25 modules.
(1) PCCPU in the MELSECNET(It)
0 Master/Local stations:
Can communicate all data (device memory, programs, etc.).
0 Remote I/O station:
Can communicate only special-function module’sbuffer data.
(2) PCCPU
in the MELSECNET/B
0 Master/Local stations:
Can communicate all data (device memory, programs, etc.).
I 1
When a computer is connected to
a local station:
When a computer is connected to
a master station for the third tie:
n
When a computer is connected to
a third-tier local station:
@-@J
The station that can send/mceive data does ne4 vq even if the aecond tier uses a MELSECNETB
and the thirdtier uses a MELSECNET (11).
1-9
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1. GENERAL DESCRIPTION
MELSEC-A
1.1.4 Mode switching function
After the AJ71C24 has started operating, the AJ71C24's RS-232C/RS422
interfaces can be switchedto another mode.
bprotocd mode
Ween formats 1 to 4
Bidirectional mode
1.1.5 Transmission control function
Data communications between the AJ71C24 and an external device can be
controlled by using DC codes
or DTR/DSR signals.
(1) Controlusing DCl/DC3 orDC2/DC4 codes
*This function can be used for controlling data communications with
an external device connected to theAJ71C24 at the RS-232C/RS-422
interface.
e DCl/DC3control refersto using theDC1 and DC3 codes to notify the
communicating device
of the enabled/disabled stateof data receive.
e DC2/DC4 control refers to using DC2 and DC4 codes toindicate the
valid range
of sendheceive data.
e Datato besent/received must begin withDC2code and endwith DC4
code.
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(2) Controlusing DTR/DSR signals
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*This function can be used for datacommunications with an external
device connected to the AJ71 C24at the RS-232C interface.
eDTR/DSR control refers to using the DTR and DSR signals to notify
thecommunicatingdevice
of theenabled/disabled state of data
receive
of the AJ71 C24 orexternal device.
*The AJ71 C24controls theDTR signal as follows:
When data can be received: Turns
ON the DTR signal.
When data cannot be received: Turns
OFF the DTR signal.
*The AJ71 C24controls theDSR signal as follows:
When the DSR signal is
ON: Sends when send data exists.
When the DSR signal is
OFF: Sends only if the DSR is ON when send
data exists.
1-10
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