18
Precautions when Reusing Programs from Earlier Models Section 2-4
The following responses are returned when reading 121 words or 246 words
through CVM1 and CV-series CPU Unit built-in ports or CVM1/CV-series Host
Link Units.
Number of Words = 121
Number of Words = 246
The second-to-last frame contains 125 data words and the last frame contains
the terminator only. This also applies when the number of words is 246 + a
multiple of 125 (i.e., 371 words, 496 words, 621 words, etc.). For responses
containing the terminator only, “00*CR” (00 = FCS, CR = carriage return) is
returned.
Response Format for MS Command
With the MS command (STATUS READ), the response data format when
using CVM1 or CV-series built-in ports or Host Link Units, is different from the
response data format when using other Units.
When a CVM1/CV CPU Unit's built-in Host Link port or CVM1/CV Series Host
Link Unit is used and an FAL or FALS instruction has not been executed,
spaces (ASCII code 20 hex) will be included in the response data for the FAL/
FALS message. With all other Host Link Units, the FAL/FALS message data is
included in the response only when an FAL or FALS instruction has been exe-
cuted.
Using a Pre-Ver. 1.2 Serial Communications Board or Unit
The response formats are the same as described above under the heading
Using the CPU Unit's Built-in Peripheral Port or RS-232C Port.
Using a Serial Communications Board or Unit with Version Number 1.2 or Later
The Serial Communications Board or Unit’s Host Link function can be made
completely compatible with the existing PLC’s Host Link function by setting
the appropriate Host Link mode (1:N or 1:1 Host Link) and the Host Link
model compatibility mode.
Host Link Model Compatibility Selection Function
Serial Communications Boards and Units with version Ver. 1.2 and later are
equipped with a Host Link model compatibility selection function. This function
switches the Board or Unit’s Host Link specifications to match the specifica-
tions of an existing Host Link program that is being reused. The following
specifications can be switched by the Host Link model compatibility function.
• Words per Response Frame
Sets the number of data words per response frame when receiving the fol-
lowing I/O memory read commands (RR, RL, RH, RC, RD, RJ, or RG).
• Sets the response frame format for the STATUS READ command (MS),
which varies when an FAL or FALS instruction has not been executed.
1
st
frame 2
nd
frame
121 words 0 words (terminator only)
1
st
frame 2
nd
frame 3
rd
frame
121 words 125 words 0 words (terminator only)
To Next Page
Loading...
Need help?
General
