Technical Reference Manual-XPM3m Revision Date: August 2014
The master controller initiates MODBUS commands to up to three other E3152202 boards connected on a RS485
network to gather digital input status information from each board. The master controller transfers digital input
status information for itself and for up to three other E3152202 boards using a digital input handshake with the
existing controller. The frequency generator output transfers digital input status data as one nibble at a time (4 bits)
to a counter input on the existing controller. There is a special frequency output setting that serves as an identity
stamp to mark the very first nibble of the possible 16 nibbles that are sent. The existing controller momentarily sets
a digital output that is connected to a digital input on the E3152202 board serving as a Master. This is to signal that
a frequency has been read correctly and to prompt the Master to send the data for the next nibble or the identity
stamp depending on where the Master controller is in the send sequence. The existing controller checks the
counter input once a second and signals the Master to send data for the next nibble when the past and current
counter values are equal, which is typically 4 seconds. It takes 68 seconds to transfer all of the digital input status
information for four E3152202 boards.
Table 1.0
Board address offset 0, board functions as a
master on a MODBUS network and initiates
MODBUS commands to other boards on the
network
Board address offset 1, board functions as a slave
on a MODBUS network
Board address offset 2, board functions as a slave
on a MODBUS network
Board address offset 3, board functions as a slave
on a MODBUS network
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