PNI TCM 5 - Manual (Page 29)

PNI Sensor Corporation Doc #1007537 r12
TCM3 & TCM5 User Manual – Sept 2012 Page 29
4.3 Binary Protocol
– RS232 Interface
4.3.1 Datagram Structure
Transport Layer for RS-232 communication:
ByteCount
(UInt16)
Packet Frame
(1 - 4092 UInt8)
CRC-16
(UInt16)
Payload
(1 - 4091 UInt8)
Frame
ID
(UInt8)
Note:
1. ByteCount is the total number of bytes in the packet including the CRC-16
2. CRC-16 is calculated starting from the ByteCount to the last byte of the Packet Frame (see in-
cluded C function at end of document).
3. ByteCount and CRC-16 are always transmitted in BIG ENDIAN.
4.3.2 Parameter Formats
Floating Point
The floating-point based parameters are in the IEEE standard format, ANSI/IEEE Std 754-1985.
64-Bit (double precision floating point)
Shown below is the 64-bit float format in big endian, in little endian bytes are in reverse order in 4
byte groups (ie: big endian:ABCDEFGH little endian: DCBA HGFE).
Exponent S Mantissa
63 62 52 51 0
The value (v) is determined as (if and only if 0 < Exponent < 2047): v = (-1)
S
* 2
(Exponent-1023)
* 1.Mantissa