Rockwell Automation 57C442 Data Highway Plus Interface Module - Manual (Page 20)

4-2
4.1.1 Status and Control Registers
The status and control registers are described in figure 4.2. Registers
4-31 are read-write registers from the host (AutoMax Processor);
registers 32-63 are read-only.
R/W Reg# Description
R/W 4 Clear Diagnostic Counters. If this register is set to a non-zero
value, the module software will clear the contents of the Data
Highway Plus diagnostic counters (registers 40-57). The module
software will then clear this register to indicate the counters have
been cleared. This register can be written to at any time.
R/W 5 Module Control. When set to 1, bit 0 of this register is used by the
user to enable the module. No communication can take place
until this bit is set. You should wait at least two seconds after
enabling the module before you send any messages on the
network. Bit 0 will be reset by the module on a hardware or
software reset. Bits 1-15 are reserved for future use.
R/W 6 Message Timeout (in 100 msec. increments). The default value is
150 (5 seconds). The value can range from 1 to 254. If a reply to
a message is not returned within this time period, the module will
return an error via the GATEWAY_ CMD_OK@ function. This
value can be changed at any time.
R/W 7 Data Highway Plus options. Bits in this register must be set
before you go on-line.
Use bits 0 and 1 to set the Data Highway Plus baud rate.
For this baud: Set:
57.6 Kbaud bit 0 to 0
bit 1 to 0
115.2 Kbaud bit 0 to1
bit 1 to 0
230.4 Baud bit 0 to 0
Bit 8 is used to enable transmission of this station’s global data. If
this bit is set to 1, the station’s global data is transmitted with the
token. The default is 0 (transmission of global data disabled). If bit
12 is set to 1, messages to stations which are off-line are not
transmitted on the network, but are returned immediately to the
module with an error code “17”. This minimizes disruptions to the
network. The default for this bit is 0 (transmission to off-line
stations enabled), which is consistent with the operation of A-B
PLCs. In this case, the module will ret
urn error ”12” when a message is sent to an
off-line station.
The remaining bits are reserved for future use.
R/W 8-12 Station Name. The user can write a station name consisting of up
to eight ASCII characters plus a null terminator. If the name is
eight characters long, the terminator is not required. However, if
the name contains fewer than eight characters, the terminator
must be included. The default station name is “AutoMax.”
13-21 Not used.
R/W 22 Response Poll Period (in units of 1/8 second). This register is
used by the GATEWAY_CMD_OK@ function to compute the
time interval to poll for command complete. The default value is 1,
which corresponds to a response polling period of 0.125 second.
23-31 Not used.
Figure 4.2 – Status and Control Register Assignments