IBM PC CONVERTIBLE Technical Reference page 175

Printer Interrupt Hex 17 (PRT_IO)
0170
0170
0171
0172
0173
0174
0175
0176
0179
017B
017F
0181
0185
0187
0189
018B
0180
018F
0191
0193
FB
IE
52
56
51
53
E8 0000
8B F2
; - - - I NT 17 H - - - - - - - - - - - - - - - - - - -- - - - - - - - -- - - - - - - -- - - - - - - - - - - - - - - - - -- --
PRLIO
THIS ROUTINE PROVIDES COMMUNICATION WITH THE PRINTER
INPUT
(AH) =0 PRINT THE CHARACTER IN (AL)
ON RETURN, AH=l IF CHARACTER COULD NOT BE PRINTED
(TIME OUT). OTHER BITS SET AS ON NORMAL STATUS CALL
(AH) =1 INITIALIZE THE PRINTER PORT
RETURNS WITH (AH) SET WITH PRINTER STATUS
(AH)=2 READ THE PRINTER STATUS INTO (AH)
7 6 5 4 3 2-1 0
I I I I I I_TIMEOUT
I I I I I_UNUSED
I I I
1_
1 I (0 ERROR
I I
1_
1 SELECTED
I
1_
1 = OUT OF PAPER
1_
1 = ACKNOWLEDGE
= NOT BUSY
(AH)=OTHER
NO ACTION TAKEN.
(OX) = PRINTER TO BE USED (0,1,2) CORRESPONDING TO ACTUAL
VALUES IN PRINTEILBASE AREA
DATA AREA PRINTER_BASE CONTAINS THE BASE ADDRESS OF THE PRINTER
CARD(S) AVAILABLE (LOCATED AT BEGINNING OF DATA SEGMENT,
408H ABSOLUTE, 3 WORDS).
DATA AREA PRINLTIM_OUT (BYTE) MAY BE CHANGED TO CAUSE DIFFERENT
TIME-OUT WAITS. DEFAULT=20.
IF NO PRINTER ATTACHED OR INVALID FUNCTION CODE RECEIVED, A RETURN
IS MADE WITH AH= PRINTER TIMEOUT (01)
REGISTERS USED
AH IS MODIFIED
ALL OTHERS UNCHANGED
INTERRUPTS:
INTERRUPTS ARE ENABLE UPON ROUTINE ENTRY, RESTORED ON EXIT.
ASSUME CS: ROMCODE, OS: DATA
PRLIO PROC FAR
STI SHIELDS DOWN
PUSH
OS
SAVE SEGMENT
PUSH OX SAVE REGISTERS USED HERE
PUSH SI
PUSH CX
PUSH BX
CALL DDS ; BIOS DATA SEG TO OS
MOV SI,DX ; GET PRINTER PARM
8A 9C 0078 R MOV BL,PRINLTIM_OUT[SI] ; LOAD TIME-OUT PARM
01 E6 SHL SI,l WORD OFFSET INTO TABLE
8B 94 0008 R MOV OX, PRINTER_BASE [SI] GET BASE ADDRESS FOR PRINTER
OB 02 OR DX,DX ANY PRINTERS PRESENT?
74 OC JZ BO NO,SIGNAL ERROR
OA E4 OR AH,AH TEST FOR (AH) =0
74 10 JZ B2 YES, PRINT CHAR
FE CC DEC AH TEST FOR (AH)=l
74 57 JZ B8 YES, INIT PRINTER
FE CC DEC AH
TEST FOR (AH) =2
74 3F
JZ B5 YES, GET STATUS
INVALID COMMAND OR NO PRINTER ATTACHED; SIGNAL TIMEOUT
2-150 ROM BIOS