191
Enhanced Protocol Macro Functions
Section 5-6
5-6-1
Data Exchange Timing for Link Words
Link word specification (a method of specifying the common area for data
exchanged between the CPU Unit and the Board/Unit) is used as a method
for specifying the storage location of send/receive data when executing com-
munications sequences in protocol macro mode.
Pre-Ver. 1.2 Units
The link word area is refreshed between the CPU Unit and Board/Unit during
every CPU Unit cycle. The actual refresh timing with the CPU Unit, however,
does not correspond to whenever the I/O is refreshed. I/O refresh is per-
formed when a request is received from the Board/Unit (according to the
send/receive command executed in the communications sequence, and
therefore not synchronized with the CPU Unit scantime). This is called on-
request I/O refreshing.
Therefore, when a send command is executed ((1) in the above diagram), the
read processing of data using variables from the I/O memory addresses in the
CPU Unit specified in the link words is performed at the start of I/O refreshing
(2). The send message is compiled based on this data (3), after which the
actual message is sent (4). As a result, the actual message send timing is not
when the send command is executed, but waits until the next I/O refresh with
the CPU Unit.
Unit Ver. 1.2 or Later
The refresh between the CPU Unit and Board/Unit is the same as in earlier
models as far as being the CPU Unit’s refresh timing. I/O refresh with the CPU
Unit, however, is continuous during execution of the PMCR(260) instruction,
regardless of any request from the Board/Unit. When the send/receive com-
mand is executed, the data from within the Board/Unit is accessed and
exchanged. This method is called continuous I/O refresh and is set in the
Setup Area allocated in the DM Area.
CPU Unit
Ladder program
I/O memory
Receive data
Send data
Board/Unit
Step 0
Step 1 (send)
(2)
(1)
Ex
ecution
IN
OUT
Receive data
Send data
I1
O1
Read and compile message
(4) Send
R (O1, 2)
Link word 1
PMCR
Communications
sequence
Earlier models refresh I/O when a request is
received (using send/receive commands in the
communications sequence).
(1) to (4) are performed in
order for the processing within
this dotted line.
Send message according
to send command
Summary of Contents for SYSMAC CJ1W-SCU21-V1
Page 3: ...iv...
Page 5: ...vi...
Page 9: ...x...
Page 15: ...xvi...
Page 89: ...60 Basic Operating Procedure Section 1 9...
Page 151: ...122 RS 232C and RS 422A 485 Wiring Section 3 4...
Page 173: ...144 Host Link Function for Replacing Existing PLCs Section 4 6...
Page 223: ...194 Enhanced Protocol Macro Functions Section 5 6...
Page 277: ...248 Communications Frames Section 6 8...
Page 291: ...262 Basic Operating Procedure in No protocol Mode Section 7 4...
Page 301: ...272 Auxiliary Area and CIO Area Allocations Section 8 3...
Page 391: ...362 Introduction Appendix A...
Page 421: ...392 CompoWay F Master Protocol Appendix B...
Page 513: ...484 E5 K Digital Controller Read Protocol Appendix F...
Page 571: ...542 E5ZE Temperature Controller Write Protocol Appendix I...
Page 587: ...558 E5 J Temperature Controller Protocol Appendix J...
Page 627: ...598 ES100 Digital Controller Protocol Appendix K...
Page 661: ...632 V500 V520 Bar Code Reader Protocol Appendix M...
Page 697: ...668 3Z4L Laser Micrometer Protocol Appendix N...
Page 717: ...688 Visual Inspection System Protocol Appendix O...
Page 755: ...726 V600 V620 ID Controller Protocol Appendix P...
Page 763: ...734 Hayes Modem AT Command Protocol Appendix Q...
Page 767: ...738 Changing Communications Port Settings Using STUP 237 Appendix R...
Page 781: ...752 Revision History...