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OBID i-scan
®
System-Manual
ID ISC.MR/PR/PRH101
FEIG ELECTRONIC GmbH
Page 18 of 131
H60301-3e-ID-B.doc
Start bits:
1
Data bits:
8
Stop bits:
1
Parity:
even (default)
odd
none
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:
..
Reaction time
Starting delay
..
..
Õ
5...n ms
Ö
Õ
min. 5 ms
Ö
Host
←
Reader:
..
..
..
Data timeout:
Within one protocol, the characters have to follow each other in intervals of maxi-
mum 12 ms.
Õ
max. 12 ms
Ö
Õ
max. 12 ms
Ö
Õ
max. 12 ms
Ö
Host
→
Reader:
Char n
Char n+1
Char n+2
..
2.2. CRC16 Calculation Algorithm
Polynom:
x
16
+ x
12
+ x
5
+ 1
⇒
CRC_POLYNOM = 0x8408;
Start Value:
0xFFFF
⇒
CRC_PRESET = 0xFFFF;
C-Example:
unsigned int crc = CRC_PRESET;
for (i = 0; i < cnt; i++)
/* cnt = number of protocol bytes without CRC */
{
crc ^= DATA[i];
for (j = 0; j < 8; j++)
{
if (crc & 0x0001)
crc = (crc >> 1) ^ CRC_POLYNOM;
else
crc = (crc >> 1);
}
}