PAL20X8                                   PAL DESIGN SPECIFICATION
P7034                                     DICK JONES      07/07/81
PRINTER DATA REGISTER/MUX
MMI FIELD APPLICATIONS ENGINEER LOMBARD, ILLINOIS
WRITE D5 D4 D3 D2 D1 D0 READ NC BUSY PAPER GND
/EN D6 PD0 PD1 PD2 PD3 PD4 PD5 PD6 PD7 D7 VCC


IF (READ) /D7  = /BUSY       ;READ PRINTER STATUS - BUSY

         /PD7 := /D7         ;LOAD MSB TO PRINTER

         /PD6 := /D6         ;LOAD PRINTER

         /PD5 := /D5         ;LOAD PRINTER

         /PD4 := /D4         ;LOAD PRINTER

         /PD3 := /D3         ;LOAD PRINTER

         /PD2 := /D2         ;LOAD PRINTER

         /PD1 := /D1         ;LOAD PRINTER

         /PD0 := /D0         ;LOAD LSB TO PRINTER

IF (READ) /D6  = /PAPER      ;READ PRINTER STATUS - PAPER OUT


FUNCTION TABLE

WRITE BUSY PAPER READ D7 D6 D5 D4 D3 D2 D1 D0 PD7 PD6 PD5 PD4 PD3 PD2 PD1 PD0

;WBPR DDDDDDDD PPPPPPPP
;RUAE 76543210 DDDDDDDD
;ISPA          76543210
;TYED
;E R                         COMMENTS
-------------------------------------------------
 LHLH HLXXXXXX XXXXXXXX      READ PRNTR STATUS
 LLHH LHXXXXXX XXXXXXXX      READ PRNTR STATUS
 CXXL ZZXXXXXX XXXXXXXX      TEST HI-Z
 CXXL LLLLLLLL LLLLLLLL      LOAD DATA TO PRINTER
 CXXL HLHLHLHL HLHLHLHL      LOAD DATA TO PRINTER
 CXXL HHHHHHHH HHHHHHHH      LOAD DATA TO PRINTER
-------------------------------------------------


DESCRIPTION

REGISTERED DATA FROM THE SYSTEM BUSS IS PRESENTED TO THE PRINTER WHEN A WRITE
STROBE FROM THE DECODER IS PRESENT (DJPR1).

PRINTER STATUS DATA (PRINTER BUSY AND OUT OF PAPER) IS TRANSFERED
TO THE SYSTEM DATA BUSS WHEN A READ STROBE FROM THE DECODER IS PRESENT.

THIS IS THE SECOND IC OF THE 2-PAL PRINTER INTERFACE FOR THE
STANDARD CENTRONICS-TYPE PRINTER.