4 |
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 view.
Example Command Block
Retrieve detailed channel status for channel 5. Store the Detailed Channel Status words to Registers
The term local PLC is used here to identify the
| Dec | (Hex) |
|
Word 1 | 00004 | (0004) | Length of Channel Command Data Block (4 words) |
Word 2 | 00000 | (0000) | Always 0 |
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
(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
TCP/IP Ethernet Communications User's Manual ± January 1996 |
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