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TCP/IP Ethernet Communications User’s Manual - August 1997 GFK-1084B
Retrieve Detailed Channel Status (2002)
The Retrieve Detailed Channel Status command requests that the current Detailed
Channel Status words be returned for a channel. The Detailed Channel Status words
contain an active/inactive channel indicator and the last channel error codes seen (see
Section 4 for more details). These two words of detailed status supplement the
information available in the COMMREQ Status word and the Channel Status bits. The
command has no effect on the value of the Channel Status bits.
Be aware that the Detailed Channel Status words are updated every time the status of
the channel changes. If, for example, the channel is operating with a fast repetition
period, the status words may change faster than the ladder executes the COMMREQ to
retrieve them. Therefore, some status values will be missed from the ladder’s point of
Example Command Block
Retrieve detailed channel status for channel 5. Store the Detailed Channel Status words
to Registers 100-101. Return the COMMREQ Status word to %R10.
Word 1 00004 (0004) Length of Channel Command Data Block (4 words)
Word 2 00000 (0000) Always 0 (no-wait mode request)
Word 3 00008 (0008) Memory Type of CRS word (%R)
Word 4 00009 (0009) CRS word address minus 1 (%R10)*
Word 5 00000 (0000) Reserved
Word 6 00000 (0000) Reserved
Word 7 02002 (07d2) Retrieve Detailed Channel Status Command number
Word 8 00005 (0005) Channel number 5
Word 9 00008 (0008) Local PLC - Memory type to store Detailed Chan. Stat. (%R)
Word 10 00100 (0064) Local PLC - Starting address (%R100)
* Word 4 (CRS word address) is the only zero-based address in the Command Block.
Only this address requires subtracting 1 from the intended address.
(Word 7) Channel Command Number: The command parameter in Word 7 requests that
Detailed Channel Status words be returned. If the command is processed successfully,
the Detailed Channel Status words will be written to the location specified in Words 9
and 10. Then the CRS word will indicate successful completion of the command. If the
specified channel is not currently in use, the latest status will be returned.
(Word 8) Channel Number: The channel number in Word 8 specifies the channel whose
status is to be read. This value must be a channel number in the range of 1 to 16 decimal.
(Word 9) Local PLC - Memory Type: Words 9 and 10 specify the starting point in the
client CPU memory where the Detailed Channel Status words are to be written. The
length of the transfer is implied and is equal to 2 words. Section 4 describes the format
of the DCS words. Word 9 specifies the memory type (See Table 3-2).
The term local PLC is
used here to identify the
client PLC-the PLC
that initiates the