Crc16 Calculation Algorithm - Feig Electronic OBID i-scan ID ISC.PR101 Manual

®
OBID i-scan
Start bits:
Data bits:
Stop bits:
Parity:
Timing conditions:
Starting delay:
Before sending a starting sign (length byte) of a protocol, there must be a delay of
minimum 5 ms.
Host → Reader:
Host ← Reader:
Data timeout:
Within one protocol, the characters have to follow each other in intervals of maxi-
mum 12 ms.
Host → Reader:

2.2. CRC16 Calculation Algorithm

16
Polynom: x + x
Start Value: 0xFFFF
C-Example:
unsigned int crc = CRC_PRESET;
for (i = 0; i < cnt; i++)
{
crc ^= DATA[i];
for (j = 0; j < 8; j++)
{
}
}
FEIG ELECTRONIC GmbH
1
8
1
even (default)
odd
none
.. Reaction time
5...n ms
max. 12 ms
Char n
+ 1 ⇒ CRC_POLYNOM = 0x8408;
12 5
+ x
⇒ CRC_PRESET = 0xFFFF;
/* cnt = number of protocol bytes without CRC */
if (crc & 0x0001)
crc = (crc >> 1) ^ CRC_POLYNOM;
else
crc = (crc >> 1);
System-Manual
.. .. ..
max. 12 ms
Char n+1
Page 18 of 131
ID ISC.MR/PR/PRH101
Starting delay
min. 5 ms
max. 12 ms
Char n+2
H60301-3e-ID-B.doc
.. ..
..