User`s manual

GFK-2334A Chapter 5 PROFIBUS Master Status and Diagnostics 5-19
5
DP-V1 Read Request (7)
The DPV1 Read Request Block is used by the master to perform a DP-V1 Read Request
to a slave device. The Command/Response format of this block is as follows.
DP-V1 Read Request Command Block – Basic Example
The following command block accomplishes the following:
Send DP-V1 Read Request to Station Address 1, Slot 2, Index 1:
Return the COMMREQ Status Word to %R10—%R13.
Return the Device Status to %R251—%R257+x.
Word Dec (Hex) Definition
1 7 (0007) Length of command Data Block
2 0 (0000) Always 0 (no-wait mode request)
3 8 (0008) Memory type of COMMREQ status word (%R)
4 9 (0009) COMMREQ status word address minus 1 (%R10)
5 0 (0000) Reserved
6 0 (0000) Reserved
7 7 (0007) DP-V1 Read Request Command
8 8 (0008) Memory type to write response (%R)
9 250 (00FA) Starting Address to write response (response written to %R251)
10 6+x
(0006+x)
Size of the response plus the size of the expected DPV1 data from the
slave (x ranges from 1 to 120 (Words).
11
1 (0001) Slave Address (ranges from 0 to 125)
12
2 (0002) Slot Number (ranges from 0 to 254)
13
1 (0001) Index (ranges from 0 to 254)
(Word 7) Command Code: Word 7 specifies the Command code for the COMMREQ to
be executed. DP-V1 Read Request = 7
(Word 8) Local PLC - Memory Type: Words 8—9 specify the location in the PLC where
the response will be written. Values for Word 8 are listed on page 5-5.
(Word 9) Local PLC - Memory Starting Address: Word 9 is a 0-based offset that
determines the starting address in the local PLC in which the response is to be written.
The value entered is the offset (0-based) from the beginning of PLC memory for the
memory type and mode specified in Word 8. This offset will be either in bits, bytes, or
words depending on the mode specified (for example, if Word 8=16 and Word 9=2, then
the starting address will be %I17). Valid ranges of values depend on the PLC’s memory
ranges.
(Word 10) Size of Response: Word 10 specifies the length of the expected response.
The length is always 6 words at a minimum plus the actual DP-V1 data length x. x ranges
from 1 to 120 words. For example, if the expected length of the DP-V1 response
COMMREQ is 8 words, word 10 should be 6 + 8 = 14.
(Word 12 and 13) Slot and Index: Slot and Index depend on the specific slave device.
Please refer to the user documentation of that slave for further details. Slot ranges from 0
to 254; Index ranges from 0 to 254.