Control And Status Registers; General; Handshaking Procedure - HMS Anybus Communicator User Manual

14. Control and Status Registers

14.1 General

The Control and Status Registers are disabled by default, but can be enabled using ACM (see "Control/
Status Word" on page 25). These registers form an interface for exchanging status information between
the sub-network and the fieldbus control system.
The main purpose of these registers is to...
• Report sub-network 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.
Anybus Communicator PROFINET User Manual
Read Status Register
Start
Yes
CR_HS_CONFIRM=
SR_HS_SEND?
No
Read Status Register
Set CR_HS_CONFIRM
to SR_HS_SEND
Done
Write to Control Register
Start
No
SR_HS_CONFIRM=
CR_HS_SEND?
Yes
Write to Control Register
Toggle CR_HS_SEND
Done
Doc: HMSI-27-309, Rev. 3.11
Chapter 14