VeriFone MX800 series Programmer's Manual page 37

The status byte (s1,s2,s3) can have one of the following values:
0
1
2
3
4
5
The returned error status may not reflect the exact cause because the algorithm
NOTE
tries to decode data in both direction streams. An error in one direction stream
may not produce the same error as in the other.
The decode algorithm searches the entire data stream for the start sentinel.
Return Values
> = 0
< 0
valid data
no data
missing start sentinel or insufficient data
missing end sentinel or excessive data
missing BCC or BCC error
parity error
Total number of bytes read
Error
D
X
M 800 S P
ERIES ROGRAMMERS
D
EVICE RIVERS
msrRead
37
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UIDE