Inter Processor Communication Packet Description; Figure 9: Sensor-Radio Inter-Processor Interface - Honeywell ISA100 Gen X User Manual

5.3 Inter Processor Communication Packet description

SPI_IPC Physical Layer Packet Format
The SPI_IPC supports a simple physical layer packet that consists of a sync byte, a data
length byte, and a CRC.
Sync Byte
5A
The SPI provides full duplex operation so that a packet can be sent from the Sensor at the same
time a packet is being sent to the Radio. The SPI transfer starts by the Radio selecting the
Sensor board using the Sensor select line. This select line indicates the start of a packet transfer
to the Sensor. The Sensor then loads a 5A sync byte into the transmit
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Figure 9: Sensor-Radio Inter-Processor Interface

IPC Data Length
N
ISA100 Gen X Radio Module User's Guide
Honeywell
IPC Data
1-n Bytes 2 bytes
CRC-16
Release Independent
April 2018