Sharp ER-A470 User Manual

CHAPTER 5. RS-232 PROTOCOL
1. Basic protocol specification
1) Data transmission from the host to a satellite
ACK
EOT
( 1 ) Inquines of the satellite.
( 4 ) Receives ACK.
( 5 ) Sends the text.block.
( 7 ) Resends the text block if NAK is received.
Resends the text block up to two times.
Sends EOT and terminates the operation
with error if NAK is still received after the
second resending of text block.
( 9 ) Sends the next text if ACK is received and
sends EOT and waits for ENQ.
( 2 ) Receives ENQ.
Checks the terminal No.
to see if it is its own.
( 3 ) Sends ACK.
( 6 ) Receives text.
Checks the check sum,text
data,etc. And goes to (8)
if there is no error in them.
( 8 ) Sends ACK.
( 10 ) Terminates the operation if EOT
is received.
ENQ
Host Satellite
Dummy
(3bytes)
Terminal No.
(6bytes)
Start code Text (parameter) End code
Text (DATA)
NAK
ACK
( 8 )' Sends NAK if any error
occurs.
ENQ
ACK
Continued on the
next page
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Sharp ER-A470 Specifications

General

Brand	Sharp
Model	ER-A470
Category	Cash Register
Language	English