mirror of
https://github.com/RevCurtisP/C02.git
synced 2024-06-08 21:29:30 +00:00
68 lines
2.3 KiB
Plaintext
68 lines
2.3 KiB
Plaintext
; Vera Layer Control Assembly Language Routines for C02
|
|
; Requires External Routines GETMEA, GETMBX, GETTBS,
|
|
; and External Variables TEMP0,TEMP1,TEMP2
|
|
|
|
;getvca(layer, index) - Get Vera Character Address
|
|
;Args: A = Layer (0/1)
|
|
; Y = Character Index
|
|
;Sets: TEMP0 = Bank
|
|
; TEMP1 = Address LSB
|
|
; TEMP2 = Address MSB
|
|
;Returns: A = Bank
|
|
; Y = Address LSB
|
|
; X = Address MSB
|
|
GETVCA: PHA ;Save Layer Number
|
|
STY TEMP1 ;Set Offset LSB to Index
|
|
LDA #0 ;Set Offset MSB to Zero
|
|
ASL TEMP1 ;Multiple Offset by 2
|
|
ROL
|
|
STA TEMP2 ;and Store MSB
|
|
PLA ;Restore Layer Number
|
|
JSR GETTBS ;Get Tile Base
|
|
TXA ;Add Tile Base LSB
|
|
CLC
|
|
ADC TEMP1 ;to Offset LSB
|
|
STA TEMP1
|
|
TYA ;Add Tile Base MSB
|
|
ADC TEMP2 ;to Offset MSB
|
|
STA TEMP2
|
|
LDA #0 ;Set Bank
|
|
ADC #0 ;to Carry
|
|
STA TEMP0
|
|
LDX #2 ;Set Count to 2
|
|
JMP ASLADR ;and Shift Address Left
|
|
|
|
;getvcd(layer, index) - Read Vera Character Data to Array
|
|
;Args: A = Layer (0/1)
|
|
; Y = Character Index
|
|
;Uses: DSTLO,DSTHI = Address of Array
|
|
;Destroys: TEMP0,TEMP1,TEMP2
|
|
;Returns: A = Number of Bytes Read
|
|
GETVCD: JSR SETVAC ;Set Vera Address to Character Address
|
|
LDA #8 ;Set Byte Count to 8
|
|
JMP GETMEA ;and Read Bytes into Array
|
|
|
|
;setvac(layer, index) - Set Vera Address to Character Address
|
|
;Args: A = Layer (0/1)
|
|
; Y = Character Index
|
|
;Sets: TEMP0 = Bank
|
|
; TEMP1 = Address LSB
|
|
; TEMP2 = Address MSB
|
|
;Returns: A = Bank + Auto-Increment
|
|
; Y = Address LSB
|
|
; X = Address MSB
|
|
SETVAC: JSR GETVCA
|
|
ORA #$10 ;Set Auto-Increment to 1
|
|
JMP SETADR ;and Set Vera Address
|
|
|
|
;setvcd(layer, index) - Write Vera Character Data from Array
|
|
;Args: A = Layer (0/1)
|
|
; Y = Character Index
|
|
;Uses: SRCLO,SRCHI = Address of Array
|
|
;Destroys: TEMP0,TEMP1,TEMP2
|
|
;Returns: A = Number of Bytes Read
|
|
GETVCD: JSR SETVAC ;Set Vera Address to Character Address
|
|
LDA #8 ;Set Byte Count to 8
|
|
JMP SETMEA ;and Read Bytes into Array
|
|
|