HT-CM400 NXP Semiconductors, HT-CM400 Datasheet - Page 10

• Manufacturer Part Number: HT-CM400
• Description: Ht Cm400; Ht Rm440 Family; Ht Rm800 Family Interface Protocol Reader - Host
• Manufacturer: NXP Semiconductors

Communication Reader-Host
3 Communication Reader-Host
3.1 Introduction
The host (e.g. PC) communicates with the contactless 125 kHz read/write device via a serial
interface using a baud rate of 9600 baud.
Data transfer details are: 1 start bit, 8 data bits, 1 stop bit and no parity bit, the Least Significant
Bit is sent first.
Each communication sequence consists of a block of bytes sent by the host, and a block of bytes
answered by the reader.
All bytes are transmitted transparently, i.e. you can use any character between 0x00 and 0xFF.
Block Length:
Block Length is the sum of all transferred bytes including Block Length but excluding BCC.
Block Title:
The Command Byte if sent from host to reader.
The Status Byte if sent from reader to host.
Data:
Data bytes are only transmitted if data is transferred.
BCC:
The BCC (Block Check Character) is calculated by bytes 1 to n-1 (n=number of bytes of the
whole communication sequence).
A different BCC calculation in Operating Mode (mode of the reader for using standard
commands) and in KeyInit Mode (mode of the reader device for using personalization commands)
helps to avoid the overwriting of secret data accidentally.
BCC calculation in Operating Mode of the reader:
BCC calculation in KeyInit Mode of the reader:
Htswp.doc/HS
The BCC is computed by EXOR-operation of all block data bytes including Block
Length.
EXOR for 1 Bit:
The BCC is computed by adding all block data bytes including Block Length. The least
significant eight bits are used as BCC.
A
0
0
1
1
B
0
1
0
1
EXOR
0
1
1
0
Example for command GetSnr:
Byte 1: Block Length
Byte 2: Command Byte
Byte 3: BCC
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Rev. 1.0
0000 0010
0100 0111
0100 0101
0x02
0x47
0x45
98-02-10