Specifications

Application Examples
PARALLEL PORT PROCEDURE
;
; THE ZT 8832 INCLUDES THREE PARALLEL PORTS. THE PARALLEL PORT
; OUTPUTS ARE ENABLED AND DISABLED WITH THE OUT2 BIT OF THE
; 82050 SERIAL PORT TO PREVENT GLITCHES DURING POWER-UP. THE
; POWER-UP STATE OF OUT2 IS A LOGICAL 0 THAT DISABLES THE
; PARALLEL PORT OUTPUTS. PASSIVE TERMINATION MAINTAINS A TTL
; HIGH ON THE PARALLEL I/O SIGNALS AT CONNECTOR J1 WHEN THE
; PARALLEL PORTS ARE DISABLED. BEFORE THE PARALLEL PORTS CAN
; BE USED, THE OUT2 BIT MUST BE PROGRAMMED. SINCE THE PARALLEL
; PORT BITS DO NOT POWER UP INITIALIZED, IT IS RECOMMENDED THAT
; THEY BE PROGRAMMED WITH A LOGICAL 0 BEFORE BEING ENABLED.
; THE PARALLEL PORTS ARE INVERTING, SO PROGRAMMING THEM WITH
; A LOGICAL 0 MAINTAINS THE TTL HIGH ON THE I/O SIGNALS AT
; CONNECTOR J1. THIS INITIALIZATION ALSO ENSURES THAT THERE
; IS NO CONTENTION BETWEEN THE PARALLEL PORT I/O SIGNALS THAT
; ARE DRIVEN AS INPUTS FROM EXTERNAL DEVICES. AFTER THIS
; INITIALIZATION SEQUENCE, THE APPLICATION SOFTWARE IS FREE TO
; COMMUNICATE WITH THE PARALLEL PORTS USING STANDARD INPUT
; AND OUTPUT INSTRUCTIONS, INCLUDING STRING INPUT AND OUTPUT.
;
; INPUTS: NONE
; OUTPUTS: PARALLEL PORTS ARE INITIALIZED AND ENABLED
; CALLS: NONE
; DESTROYS: FLAGS
PAR_INIT PROC
; PRESERVE REGISTER STATUS
PUSH AX
PUSH DX
; INITIALIZE PARALLEL PORTS
PUT PAR_PORT_0,PAR_PORT_INIT
PUT PAR_PORT_1,PAR_PORT_INIT
PUT PAR_PORT_2,PAR_PORT_INIT
; ENABLE PARALLEL PORTS
MOV DX,ACC_MODC
IN AL,DX
OR AL,ACC_OUT2
OUT DX,AL
; RESTORE REGISTER STATUS
POP AX
POP DX
PAR_INIT ENDP
;
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