Caple C871i Bedienungsanleitung PDF herunterladen (Seite 214)

100

101

Apple II Computer Info

The procedure for reading to an input is:

(1) Write a 0 to bit 2 of the Control Register

(2) Write 0's to the Data Direction Register of each

input bit

(3) Write a 1 to bit 2 of the Control Register

(4) Read data from the Port

Control Register A $C085+s0

Control Register B $C087+s0

Control Register C $C089+s0

Control Register D $C08B+s0

Examples:

Reading all 8 bits from Port A

LDA $C085+s0 ;Read Control Register A

AND #%11111011 ;Turn off bit 2

STA $C085+s0 ;Set CRA for Data Direction

LDX #$00 ;All bits are inputs

STX $C084+s0 ;Set Data Direction for all inputs

ORA #%00000100 ;Turn on bit 2

STA $C085+s0 ;Set CRA for Port A data

LDA $C084+s0 ;Read Port A data

Reading bits 0, 1, 2 from Port B

LDA $C087+s0 ;Read Control Register B

AND #%11111011 ;Turn off bit 2

STA $C087+s0 ;Set CRB for Data Direction

LDX #%11111000 ;Bits 0, 1, 2 are inputs

STX $C086+s0 ;Set Data Direction

ORA #%00000100 ;Turn on bit 2

STA $C087+s0 ;Set CRB for Port B data

LDA $C086+s0 ;Read Port B data

Writing bits 4, 5, 6, 7 to Port C

LDA $C089+s0 ;Read Control Register C

AND #%11111011 ;Turn off bit 2

STA $C089+s0 ;Set CRC for Data Direction

LDX #%11110000 ;Bits 4, 5, 6, 7 are outputs

STX $C088+s0 ;Set Data Direction

ORA #%00000100 ;Turn on bit 2

STA $C089+s0 ;Set CRC for Port C data

LDA #$A0 ;Data to write

STA $C088+s0 ;Write Port C data

Writing all 8 bits to Port D

LDA $C08B+s0 ;Read Control Register D

AND #%11111011 ;Turn off bit 2

STA $C08B+s0 ;Set CRD for Data Direction

LDX #$FF ;All bits are outputs

STX $C08A+s0 ;Set Data Direction for all outputs

ORA #%00000100 ;Turn on bit 2

STA $C08B+s0 ;Set CRD for Port D data

LDA #$AE ;Data to write

STA $C08A+s0 ;Write Port D data

Apple II Computer Technical Information : Apple II Family Hardware Info

ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 214 of 572

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