lri64 STMicroelectronics, lri64 Datasheet - Page 48

• Manufacturer Part Number: lri64
• Description: Memory Tag Ic At 13.56 Mhz, With 64-bit Unique Id And Worm User Area, Iso15693 And Iso18000-3 Mode 1 Compliant
• Manufacturer: STMicroelectronics

C-example to calculate or check the CRC16 according to ISO/IEC 13239
Appendix B
22.1
48/52
The Cyclic Redundancy Check (CRC) is calculated on all data contained in a message,
from the start of the Flags through to the end of Data. This CRC is used from VCD to LRI64
and from LRI64 to VCD.
To add extra protection against shifting errors, a further transformation on the calculated
CRC is made. The One’s Complement of the calculated CRC is the value attached to the
message for transmission.
For checking of received messages the 2 CRC bytes are often also included in the re-
calculation, for ease of use. In this case, given the expected value for the generated CRC is
the residue of F0B8h
Table 20.
CRC calculation example
This example in C language illustrates one method of calculating the CRC on a given set of
bytes comprising a message.
#define
#define
#define
#define
#define
#define
void main()
{
4, 0x91, 0x39};
// calculate_or_check_crc = CHECK_CRC;// This could be an other
example
CRC Type
unsigned char array_of_databytes[NUMBER_OF_BYTES + 2] = {1, 2, 3,
unsigned int
int
int
int
calculate_or_check_crc = CALC_CRC;
if (calculate_or_check_crc == CALC_CRC)
{
}
ISO/IEC
13239
number_of_databytes = NUMBER_OF_BYTES;
POLYNOMIAL0x8408//
PRESET_VALUE0xFFFF
CHECK_VALUE0xF0B8
NUMBER_OF_BYTES4// Example: 4 data bytes
CALC_CRC1
CHECK_CRC0
C-example to calculate or check the CRC16
according to ISO/IEC 13239
CRC definition
Length
16 bits
current_crc_value;
number_of_databytes = NUMBER_OF_BYTES;
calculate_or_check_crc;
i, j;
X
16
+ X
12
+ X
Polynomial
5
+ 1
CRC definition
x^16 + x^12 + x^5 + 1
= Ox8408
Direction
Backward
Preset
FFFFh
Residue
F0B8h
LRI64