IBASE Technology MPT-1000V, User Manual

Page: 99 / 111

Appendix
MPT-1000V User’s Manual 91
2.)
Protocol
 Signal transmit format
Bandwidth
Baud rate: 19200 bps
Data Format
Parity: No Parity
1 start bit
8 data bits
1 stop bit

Packet Format
Header Size Command Data CRC
2 bytes 1 byte 1 byte 0 – 64 bytes 2 bytes
Header
bytes indicate start of the packet.
Size specifies number of bytes for data field.
Command identifies action, which is required to be performed on the
data.
CRC verifies data integrity for header, size, command and data bytes.
 CRC
Protocol uses 16-bit CCITT CRC to verify data integrity.
P(x) = X
16 +X 12 +X 5 +1
unsigned calc_crc( unsigned char *data, unsigned n, unsigned start) {
unsigned I, k, q, c, crcval;
crcval=start;
for (I=0; I<n; I++) {
c=data(I) & 0xFF;
q=(crcval^c) & 0x0F;
crcval=(crcval>>4)^(q*0x1081);
q=(crcval^(c>>4)) & 0x0F;
crcval=(crcval>>4)^(q*0x1081);
}
return crcval;
}