Bematech MP-4000 TH Programmer's Manual - Manual (Page 83)

Appendix III - Transmission Status Identification
Because the specified status bits transmitted from the ESC/POS commands are
fixed, the user can confirm the command to which the status belongs, as shown in the
following table.
When using Auto Status Back (ASB), however, process the consecutive three-byte
code (except for XOFF) as ASB data after confirming the first byte of the ASB. Otherwise,
the status transmitted by using the GS r and the status of the second and following bytes
of the ASB cannot be differentiated.
Transmission Status Identification
Command & Function Status Reply
GS I <0**0****>B
GS r <0**0****>B
XON <00010001>B
XOFF <00010011>B
DLE EOT <0**1**10>B
ASB (1st byte) <0**1**00>B
ASB (2nd to 4th bytes) <0**0****>B