DESCRIPTION AND OPERATION
MODULE DATA
I-E96-303A
2 - 5
MODULE DATA
FC 149 in the master module configuration accesses the ASO
on the slave expander bus. Specifically, it allows the MFP to
automatically read status data and readback data from the
slave module, and write output data to it. FC 149 defines only
seven outputs; two function blocks must be linked together
(specification 2) to define all fourteen outputs. The slave
address in FC 149 must be the same as the address set on the
slave address dipswitch (S1).
Status Data
Status data is one 8-bit byte consisting of module identification
and status information. Slave module identification is in the
four most significant bits (MSB). It identifies the slave module,
and verifies the slave expander bus communication integrity
and MFP configuration.
Also included in the status byte is information concerning the
slave operating status. The MFP uses this information to deter-
mine if the slave has been removed and reinserted or powered
down or has ever had data written to it. A remove/reinsert or
power down clears default information from the slave memory.
If the status byte reflects any of these conditions, the MFP
downloads the information needed for default operation. The
LED state is read back to the MFP in the status byte to verify
proper indication.
Readback Data
This data consists of analog output readback values that the
MFP reads to verify ASO module operation. The A/D converter
changes analog output feedback signals from each output and
the reference voltages (1 VDC and 5 VDC) to analog count val-
ues. The MFP reads each of these count values once every exe-
cution cycle. It reads the fourteen readback values to allow
adjustment of the analog outputs and to check for output cir-
cuit failures. It reads the reference voltages to calibrate and
verify A/D converter operation.
Output Data
Output data is a 2-byte value consisting of an analog output
count and default values. The MFP writes this data to the
DPRAM each execution cycle for each of the fourteen outputs.
The count sets the analog outputs during normal operation.
Default values are sent to the PAL to set the outputs during a
time-out
; the default values are selected in the MFP configura-
tion (Function Code 149).
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