Centronics Printer Interface
Shared Signals
Four printer port signals on the ZT 8809A (INIT*, AFD*, ERR*, and
SLIN*) are shared by various logic functions.
Initialize (INIT*) is used to control the RS-485 drivers and is needed
for this control function only if multiple drivers are present on the
RS-485 bus. If the ZT 8809A is to be a receiver or transmitter only,
the RS-485 drivers may be disabled or enabled via hardware jumpers.
In this case, INIT control is not needed and W13B is removed. This is
the factory default configuration. Refer to Chapter 8 for further detail
on the serial ports.
Autofeed (AFD*) is used to control the write-protection feature on the
battery-backed RAM drive. This feature is controlled by STD DOS
only and is useful for protecting the RAM drive from being
overwritten by errant applications software. The RAM drive usually
contains important system parameters pertinent to STD DOS. STD
DOS enables the write signal to the RAM drive only when it needs to
update information or add files. If an application is running, the drive
remains protected. For non-DOS users, this battery-backed RAM
powers up unprotected, free for read and write access, and remains so
unless the AFD* signal is set to 1 with jumper W37 installed.
Error (ERR*) is used to drive IR2 of the programmable interrupt
controller (PIC) or the interrupt input directly into the processor. The
routing of this interrupt depends upon the configuration of jumpers
W6, W39, and W50. Refer to Appendix A for detailed jumper
descriptions.
9-10
Содержание ZT 8809A
Страница 15: ...Tables Table B 9 J5 Pin Assignments B 17 Table B 10 J6 Pin Assignments B 18 Table B 11 J7 Pin Assignments B 19...
Страница 334: ...Jumper Configurations W49 W48 A W47 B A B W37 W66 A W50 B C J7 W67 Figure A 11 W37 W47 50 W66 W67 Jumper Blocks A 34...
Страница 346: ...Jumper Configurations W61 W60 W62 W63 W64 A B A B W65 Figure A 13 W60 W65 Jumper Block A 46...