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TCP/IP Ethernet Communications User’s Manual - August 1997 GFK-1084B
Communications Status Words
The COMMREQ Status word (CRS word) and the first word of the two Detailed Chan-
nel Status words (DCS words) report status and errors in the same format, as shown be-
low. The second word of the DCS words indicates when the channel is active.
The CRS word location is specified in Words 3 and 4 of the Command Block. The DCS
words location is specified in the Retrieve Detailed Channel Status Command. The con-
tents of these status words are defined below:
The initial value of the Detailed Channel Status words is all zeros. DCS words are reset
to zero when:
The Ethernet Interface is powered up or restarted
The CPU transitions from STOP to RUN
A channel abort COMMREQ aborts the channel
Hex Format
High Low
00 00
Minor Error Codes (high byte)
Success and Major Error Codes (low byte)
CRS Word in
Figure 3-3. Format of the COMMREQ Status Word (CRS Word)
High Low
00 00
Minor Error Codes (high byte)
Success and Major Error Codes (low byte)
0000
Channel Active (0001 = channel active,
0000 = channel not active)
DCS Word in Hex Format
Word 1Word 2
Figure 3-4. Format of the Detailed Channel Status Words (DCS Words)
There are several points to remember when interpreting the contents of the COMMREQ
Status word and Word 1 of the Detailed Channel Status words:
1. Display the Status Words in hexadecimal form to more easily differentiate the high and
low bytes. A good way to do this is to use a MOVE WORD function block to display
the hexadecimal value within the ladder program.
2. The Ethernet Interface will never send a zero for the COMMREQ Status word to the
PLC CPU. The user program should zero the COMMREQ Status word before issuing