Printer Buffer Size; Parallel Port Inquire And Ieee 1284; Figure 17 Parallel Port Ack Timing Options; Table 55 Parallel-Port Timing - TransAct Ithaca 8000 Programmer's Manual

Communications
Some systems may wish to change the details of how the strobe, busy, and
acknowledged signals interact. The parallel-port option features define how the strobe,
busy, and acknowledged signals operate. In normal mode, the printer follows the
standard (Centronics) parallel-port conventions. With Options 1 and 3, the
acknowledged and busy signals change simultaneously, which is sometimes referred to
as ack-after-busy. Options 2 and 3 force busy high on the rising edge of the strobe,
which is sometimes referred to as busy-while-strobe timing. In all cases, the data is
latched on the rising edge of the strobe. In most cases, the normal timing mode gives
the best results.
Data
t1
STB
t2
BUSY
ACK-while-BUSY
ACK
ACK-in-BUSY
ACK
ACK-after-BUSY
ACK

Figure 17 Parallel Port ACK Timing Options

Legend Time Interval
t1 DATA Setup to STB
t2 STB Width
t3 DATA Hold after STB
t4 BUSY Delay after STB
t5 ACK Pulse Width

Table 55 Parallel-port Timing

Note: Altered STB timing to take data on the falling edge of STB can be generated as a
factory option.

Printer Buffer Size

®
The Ithaca 8000 printer has a configurable buffer size. It can be set from 40 to 8192
bytes. The configurable buffer allows an application to control how far ahead the buffer
gets from the printer. The smaller the buffer, the tighter the control will be. It is up to the
application developer to select the optimal buffer size.

Parallel Port Inquire and IEEE 1284

®
The Ithaca 8000 printer supports the IEEE 1284 bidirectional parallel peripheral
interface standard. The IEEE 1284 standard provides for a bidirectional link on the
parallel port. The Ithaca
nibble mode reverse channel for printer identification and status inquire commands. It is
100-06908
t3
t4
t5
®
8000 Printer only supports Modes 0 and 4, which provide a
Rev D
®
Ithaca 8000 Programmer's Guide
Minimum Maximum
0.5 uS
0.5 uS 500 uS
0.5 uS
0 0.5 uS
2.5 uS
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