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SIM2 C3X LITE
RS-232C CONTROL SPECIFICATIONS
4
3. Communication Protocol
The communication protocol is packet oriented. Packets consists of Header and Payload.
There are two types of packets: Event and Operation.
The packet header size is fixed (7 bytes), while the packet payload type and content varies based on the
type of packet: Event payload size is 6 bytes, while Operation payload size is 25 bytes.
The entire packet size is variable, being the sum of the fixed-size packet header and variable-sized packet
payload: Event packet size is 13 bytes and Operation packet size is 32 bytes.
Header
All Packets use the same Packet Header format.
The Packet Header size is fixed at seven bytes.
0 1 2 3 4 5 6
BE EF
Packet Type Packet Payload Size Packet Checksum (CRC)
0xEFBE is a fixed value that is used to insure packet alignment if there are partial packets received or byte
lost. The least-significant byte of the word (BE) is sent first, then the most-significant-byte (EF).
The Packet Type is a number (a byte in length) that defines the type of data in the packet.
The Packet Payload Size is a number (two bytes) that defines the size of the payload portion of the
packet. For a given Packet Type, Packet Size is fixed.
The Packet Checksum (two bytes) is the CRC value for the entire packet (Header and Payload).
Payload
The packet payload format depends on the packet type.
The Event packet payload size is 6 bytes, while the Operation packet payload size is 25 bytes.
Event Packet Format:
0 1 2 3 4 5
Event
00 00 00 00
Operation Packet Format:
0 1 2 3 4 5 6 7 8 9 10 11 12
Op Type
Op ID
00 00
Op Target
00 00
Op Value
00 00
13 14 15 16 17 18 19 20 21 22 23 24
00 00 00 00 00 00 00 00 00 00 00 00