Anybus Communicator Modbus plus, Руководство пользователя

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Doc.Id. SCM-1200-093
Anybus Communicator for Modbus Plus
Doc.Rev. 3.01
Chapter 14
14. Control and Status Registers
14.1 General
The Control and Status Registers are disabled by default, but can be enabled using the Anybus Config-
uration Manager (see “Status / Control Word” on page 28). These registers form an interface for ex-
changing status information between the subnetwork and the fieldbus control system.
The main purpose of these registers is to...
• Report subnetwork related problems to the fieldbus control system
• Ensure that only valid data is exchanged in both directions
• Enable the fieldbus control system to start/stop data exchange with selected nodes on the sub-
network
If enabled, these registers occupy the first two bytes in the input and output data areas (0x000-0x001 and
0x200-0x201 respectively), which means they can be accessed from the fieldbus just like any other data
in these areas.
Note: Internally, these registers are stored in Motorola-format (i.e. MSB first). If the higher level net-
work uses a different byte order, the upper and lower bytes will appear swapped.
14.1.1 Handshaking Procedure
A special handshaking procedure, which is illustrated in the two flowcharts below, must be followed
when accessing these registers to ensure that both parts receive proper information.
Start
Read Status Register
Set CR_HS_CONFIRM
to SR_HS_SEND
CR_HS_CONFIRM=
SR_HS_SEND?
Yes
Done
Start
Read Status Register Write to Control Register
Write to Control Register
Toggle CR_HS_SEND
SR_HS_CONFIRM=
CR_HS_SEND?
No
No Yes
Done