Epson TM-U950 Technical Manual page 36

CONFIDENTIAL
Precautions on receiving status from the printer
The printer status transmission is available by using the both-way communication facility in the
Nibble/Byte mode in accordance with the IEEE 1284 mode.
The following precautions must be taken for receiving the status from the printer.
Example: In the normal (wait) state, the ASB status is configured as follows:
When the following sequence of operations is performed, near end detection, cover open, cover
closed, the following pieces of data are accumulated.
When the ASB status is received following this, a total of 8 bytes of ASB will be transmitted as
follows.
Rev. A
Interfacing conditions should be all based on the TTL level. In addition, both the rise time
and fall time of each signal must be 0.5 µs or less.
Data transmission should not ignore the signal nAck or Busy. An attempt to transmit data
with either signal, nAck or Busy, ignored can cause lost data. (Data transmission to the
printer should be made after verifying the nAck signal or while the Busy signal is low.)
Interface cables should be as short as possible.
The allowable capacity of the printer's internal buffer is 100 bytes. Status signals exceeding
this capacity will be discarded. To prevent possible loss of status data, the host should
always be ready for data reception (reverse mode).
When ASB is used, the host should be in the wait state for data reception (reverse idle
mode). When this state is not available, the host should enter the reverse mode to always
monitor the presence of data.
When ASB is used, preference should be given to the ASB status for transmission over the
other status signals. Any accumulated ASB status signals left for transmission from the last
to the newest ASB status transmission should be transmitted together at one time as one
ASB status showing the change has been made, followed by the latest ASB status.
1st status 2nd status
0000 0000 0000 0000
1st status 2nd status
1 0000 0000 0000 0000
2 0010 1000 0000 0000
3 0000 0000 0000 0000
Accumulated ASB (1+2+3)
+
The latest ASB (3)
3rd status 4th status
0000 0000 0000 0000
3rd status 4th status
0000 0011 0000 0000 Near end detection
0000 0011 0000 0000 Cover open
0000 0011 0000 0000 Cover closed
1st status 2nd status 3rd status
0010 1000 0000 0000 0000 0011
1st status 2nd status 3rd status
0000 0000 0000 0000 0000 0011
Features and General Specifications 1-25
TM-U950/U950P Technical Manual
4th status
0000 0000
4th status
0000 0000