Honeywell ISA100 Gen X User Manual page 29

register for the next data transfer. The Radio starts the data transfer when it receives a
synchronization byte from the Sensor board.
When the Radio receives a 5A byte from the Sensor, it reads and sends a 5A back to the
Sensor. When this second data transfer is complete, the next type received by the Radio is the
number of bytes that the Sensor needs to send (in case sensor is the transmitter). The Radio
then compares the number of bytes it has to send and proceed to transfer maximum number of
bytes of the Sensor or Radio data.
When all the data bytes are transferred, the Radio de-asserts the Sensor select line to indicate
the end of the packet. Then both the Sensor and the Radio inspects the received bytes for a
correct CRC (discounting any received sync bytes.) If it is a valid message, the packet is passed
to the inter-processor communication application sub layer interface.
SPI_IPC Data Format
The SPI_IPC application sub layer provides processing of valid messages that have been
received over the SPI inter-processor interface. The inter-processor data processing utilizes a 4
byte header consisting of a packet class, packet type, packet ID, and packet length.
Packet Class
1 byte
Packet Class
Packet Class byte is an 8-bit value and defined as follows
Packet Class
The packet class is used for defining the basic construct of the packet. The two packet
classes supported are: ASL packets and Stack specific.
The Request-Response bit is used only for Stack specific Class packets.
Packet Type
Release Independent
April 2018
Packet Type
1 byte
4-bit
Request-Response
ASL queued packets class = 0x00
Stack specific class = 0x30 (Request) or 0x38 (Response)
ISA100 Gen X Radio Module User's Guide
Packet ID Packet
Length
1 byte 1 byte
1-bit 3-bit
Reserved
Honeywell
IPC Packet
Data
1-n Data
Bytes
29