GE VersaPoint IC220PBI002, Руководство пользователя

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8-18 VersaPoint™ I/O System Profibus-DP NIU User’s Manual – August 2005 GFK-1911B
8
Start Fragment
Byte 1
Service
Byte 2
Module number
Byte 3 Index high
Byte 4 Index low
Byte 5 Subindex
Byte 6
Length, if required
Byte 7
Data block, if required
...
Byte n
Data block, if required
Byte 1 - Service in start fragment:
7 6 5 4 3 2 1 0
Request/
response
0 0
Fragment
-ation
Action
Bit 7: Request/response
0 = Request
1 = Response
Bits 6 to 5: Fragment type
00 = Start fragment
Bit 4 Fragmentation
0 = Not fragmented
1 = Fragmented
Bits 3 to 0: Action
00
hex
No action (clear)
01
hex
Read PCP (I/O module)
02
hex
Write PCP (I/O module)
03
hex
Read (bus coupler)
04
hex
Write (bus coupler)
05
hex
Read PDU length (displayed in bytes)
06
hex
Read PCP with Invoke ID (I/O module)
07
hex
Write PCP with Invoke ID (I/O module)
08
hex
to 0F
hex
Reserved
In the start fragment, enter the Invoke ID for actions 6 and 7 (read/write with the
Invoke ID) after the module number. Bytes 3 to n are then entered at byte 4.
Actions 01
hex
and 02
hex
, and 06
hex
and 07
hex
refer to PCP; these commands can be
used to access PCP modules. Actions 03
hex
and 04
hex
are used to read or write
objects on the NIU (object indices 2 to 5).