User Manual

Coupler - Reference manual
RM 4
Version 1.0
P3: number of data bytes sent to the coupler.
Ack. : coupler acknowledgement. It is always equal to the command code, except when
an error occurs. If Acknowledgement value is different than instruction byte, then the
received byte is the first byte of a status error code coded on 2 bytes.
Data : data sent by host to the coupler. Size of data array has to be P3.
Status word : 90 00h if correct / error code.
Error : If the Acknowledgement value is different than the instruction byte, then the received
byte is the first byte of a status error code coded on 2 bytes.
Case 4 : ISO InOut Data Exchange - Host
⇔⇔
⇔⇔
⇔ coupler
Ack. Data in Ack. Data out
Host
Cla. Ins. P1 P2 P3 Data in
Coupler
= Ins. = Ins. Data out SW1 SW2
nb bytes
1 = P3 1 =P252
Command
S
tatus word
s
Class : always 80h
Instruction : command code
P1 : command parameters
P2 : number of data bytes expected from the coupler.
P3 : number of data bytes sent to the coupler.
Ack. : coupler acknowledgement. It is always equal to the command code, except when
an error occurs. If Acknowledgement value is different than instruction byte, then the
received byte is the first byte of a status error code coded on 2 bytes.
Data : data sent to the host by the coupler. Size of the command has to be P3.
Status word : 90 00h if correct / error code.
BLOCK PROTOCOL
The block mode is based on the exchange of a block sent from the host to the coupler and
after a block sent back from the coupler to the host. By this way there is no break in the
flow host-coupler. The diagram below describes this block protocol.
BLOCK
Send 5 bytes
command
CL A SS|INS|P1|P2|P3
Coupler if no
error in
processing
Send an
acknow ledge
(INS)
Return
Data
Return a
status word
Send an
optional LRC
Coupler if error
in processing
Return a
status w ord
Send an
optional
LRC
Host Send P3
Data if any
Send an
optional LRC
LRC enables the user to check is the transmission has been performed correctly. See next
paragraph for more information.
Note: Block protocol is only available on 2G version of our readers.