- 139 -
(2) Immediate termination:
1) If the interface is deactivated (IEEE 1284 Active: Low) without Event 22 having taken place, the
printer immediately performs Termination. In this termination, the data is not guaranteed, and the
printer switches the data bus from output to input within 1 µsec.
In the Reverse Idle phase, the printer can notify the host that it has data to transfer to the host. The
notification may occur simultaneously with termination in order for the host to move from the Idle
phase to the Compatibility mode.
If the printer has data to send, it initiates the Interrupt phase indicated by Events 8 and 9. In this case,
if 1284 - Active (nSelectIn) was set to Low before HostBusy (nAutoFd) changed from High to Low, the
printer interprets that the host has switched to the Termination phase, and then completes the normal
termination through handshaking.
4.3
Identification
of
Send
Status
Because the status sent from the printer has certain fixed bits, it is possible to identify to which command the
status belongs.
When using ASB (Automatic Status Back), however, the first byte of ASB should be checked, and then the
three consecutive bytes except for XOFF should be treated as ASB data.
Identification of Send Status
Command and Function
Status
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 - 4th bytes)
<0**0****>B
