Service manual

1-18 Features and General Specifications Rev. B
Confidential
Reception of status from the printer through the bidirectional parallel interface
In bidirectional parallel interface operation, printer status transmission is available using the
two-way communication facility of the IEEE 1284-compatible nibble/byte modes. In this case,
unlike in RS-232 serial interface operation, real-time interruptions from the printer to the host
are disabled, and so you must pay attention to the following.
❏
The maximum capacity of the printer’s internal buffer is 100 bytes (except ASB status).
Status signals exceeding this capacity are discarded. To prevent possible loss of status, the
host must be ready for data reception (Reverse Mode).
❏
When ASB is used, the host is preferably in the wait state for data reception (Reverse Idle
Mode). When this state is not available, the host enters Reverse Mode to continually monitor
data presence.
❏
When ASB is used, preference is given to ASB status for transmission over other status
signals. Any accumulated ASB status signals left for transmission from the last to the newest
ASB status transmissions are transmitted together at one time as one ASB status showing the
presence of change, followed by the latest ASB status.
Example: In the normal (wait) state, the ASB status is configured as follows:
In a sequence of operations including near end detection and the paper FEED button being
pressed and released, the following pieces of data are accumulated.
When ASB status is received following this, a total of eight (8) bytes of ASB will be transmitted
as follows: Accumulated ASB (
➀
+
➁
+
➂
).
First Status Second Status Third Status Fourth Status
0001 0000 0000 0000 0000 0000 0000 0000
First Status Second Status Third Status Fourth Status
➀
0001 0000 0000 0000 0000 0011 0000 0000 Near end
detection.
➁
0101 1000 0000 0000 0000 0011 0000 0000 Paper FEED
button is
pressed.
➂
0001 0000 0000 0000 0000 0011 0000 0000 Paper FEED
button is
released.
First Status Second Status Third Status Fourth Status
Accumulated ASB (
➀
+
➁
+
➂
)
0101 1000 0000 0000 0000 0011 0000 0000
+ First Status Second Status Third Status Fourth Status
The latest ASB (
➂
)
Fourth Status
0001 0000 0000 0000 0000 0011 0000 0000