Centronics Printer Interface
Select In (SLIN*) is used for SLOW/FAST control, to allow the
software to dynamically control the processor clock frequency to
conserve power in low-power CMOS applications. Processor clock
speed is switchable between 19.5 kHz and 5 MHz for the
ZT 88CT08A and 31.25 kHz and 8 MHz for the ZT 88CT09A,
provided W46B is installed. If SLIN* is needed for the printer, the
processor speed may then be controlled by jumpers W46A and B.
SLIN* is also used to map in the lower 128K memory space of 256K
EPROMs placed in socket 5D1. This means that systems requiring
the use of SLIN* as a printer port signal may not efficiently use a
256K EPROM in socket 5D1.
Whenever possible, it is preferable to leave signals INIT*, AFD*,
ERR*, and SLIN* available for STD DOS use unless the printer
requires them. As all four are treated as a group, STD DOS assumes
they are all available or all not available, according to information
described in the SYSTEM.CFG file. Most printers do not use these
signals. See the following discussion.
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