Access keyboards ATB 420/421 Multi-Function Keyboard Product Specification and Service Guide
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Rev 6
Access Keyboards 2001 & 2002 - All rights reserved Page 21 of 37
5.4
SITA Data Format
In SITA format, RS232 serial data to and from the ATB420/421 is transmitted in the form of blocks
with the following generalised format.
<SODn><STX> ..up to 1024 bytes of data..<ETX><EODn>
Where <SODn> is a Start Delimiter and <EODn> is the corresponding End Delimiter.
MNEMONIC
HEX VALUE
DESCRIPTION
STX
02
START OF TEXT. This character signals the START of BLOCK
ETX
03
END OF TEXT. This character signals the END of a
BLOCK
SOD1
0E
Start delimiter for Mag Swipe Reader
EOD1
0F
End delimiter for Mag Swipe Reader
SOD2
1C
Start delimiter for Optical Character Reader (OCR) devices
EOD2
1D
End delimiter for Optical Character Reader (OCR) devices
SOD3
1E
Start delimiter for Bar Code Reader Device
EOD3
1F
End delimiter for Bar Code Reader Device
CR
0D
Carriage Return
ESC
1B
Escape
5.4.1 MSR Data Format
When the ATB420/421 formats data read from MSR is the following data structure is used
<SOD1><STX>[DOC-ID]
[T/B] magnetic data<CR>
[T/B] magnetic data<CR>
[T/B] magnetic data<CR>
…..
[T/B] magnetic data<CR>
[T/B] magnetic data<ETX><EOD1>
MNEMONIC
ASCII
HEX VALUE
DESCRIPTION
DOC-ID
A or
C
41 or
43
An ATB document read
A credit card read
T/B
11 to 13,
21 to 23
31 to 33
41 to 43
TRACK/BLOCK NUMBER
(First digit is Track number and second is block
number)
Note:
The range for TRACK/BLOCK NUMBER is from 11 Hex to 43 Hex
The TRACK/BLOCK NUMBER identifier is only included in the message if the block has been
detected. For example, when reading a ATB stub with tracks 1 and 3 read, the data string will be:
<SOD1><STX>A 013H Data….<CR> 033H Data <ETX><EOD1>
If the Magnetic Swipe Reader detects errors in the data, it will send a zero length data block.
Block numbers for a credit card are set to 1. No <CR> is sent after the last reported block.
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