68 lines
2.9 KiB
Plaintext
68 lines
2.9 KiB
Plaintext
------- FILE D:\owncloud\Documents\Projects\RC6502\RC6502 VDU\code\VDU Alphanumeric\vdu_alphanumeric.asm LEVEL 1 PASS 2
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1 fcce processor 6502
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2 fcd0 ????
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3 fcd0 ???? 00 30 PAGECTR EQU $0030
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4 fcd0 ???? 00 31 ZPPTR EQU $0031
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5 fcd0 ???? 00 31 ZPPTR_LSB EQU $0031
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6 fcd0 ???? 00 32 ZPPTR_MSB EQU $0032
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7 fcd0 ????
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8 fcd0 ???? 80 00 VDU_BASE EQU $8000
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9 fcd0 ???? 88 00 VDU_REG_0 EQU $8800
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10 fcd0 ???? 8c 00 VDU_REG_1 EQU $8C00
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11 fcd0 ????
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12 fcd0 ???? ; Main program
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13 f000 org $F000
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14 f000 a9 00 INIT lda #$00
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15 f002 8d 00 88 STA VDU_REG_0
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16 f005 8d 00 8c STA VDU_REG_1
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17 f008
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18 f008 20 11 f0 JSR CLEAR
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19 f00b 20 33 f0 JSR SET_MOTD
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20 f00e 4c 0e f0 DONE JMP DONE
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21 f011
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22 f011 ; Clear screen routine
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23 f011 a0 80 CLEAR LDY #$80
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24 f013 a2 00 LDX #$00
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25 f015 a9 01 LDA #1
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26 f017 20 1b f0 JSR CLEAR_RAM
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27 f01a 60 RTS
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28 f01b
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29 f01b 85 30 CLEAR_RAM STA PAGECTR ;set pages to clear (1-255, 0 = 256)
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30 f01d 86 31 STX ZPPTR_LSB ;set start address LSB
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31 f01f 84 32 STY ZPPTR_MSB ;set start address MSB
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32 f021 a9 20 LDA #$20 ;clear value -- could be anything
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33 f023 a0 00 LDY #0 ;index
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34 f025
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35 f025 91 31 NEXT_BYTE STA (ZPPTR_LSB),y
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36 f027 c8 INY
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37 f028 d0 fb BNE NEXT_BYTE ;next location
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38 f02a
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39 f02a c6 30 DEC PAGECTR ;one less page to clear
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40 f02c f0 04 BEQ CLEAR_DONE ;done
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41 f02e
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42 f02e e6 32 INC ZPPTR_MSB ;next page
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43 f030 d0 f3 BNE NEXT_BYTE ;more pages remaining
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44 f032
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45 f032 60 CLEAR_DONE RTS
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46 f033
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47 f033
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48 f033 ; Write message to the display
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49 f033 a2 00 SET_MOTD LDX #0
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50 f035 bd 44 f0 NEXT_CHAR LDA MESSAGE,x
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51 f038 c9 00 CMP #0
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52 f03a f0 07 BEQ MOTD_DONE
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53 f03c
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54 f03c 9d 00 80 STA VDU_BASE,x
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55 f03f e8 INX
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56 f040 4c 35 f0 JMP NEXT_CHAR
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57 f043 60 MOTD_DONE RTS
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58 f044
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59 f044
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60 f044 0c 03 24 23*MESSAGE byte.b 12,03,36,35,30,32,20,16,04,15,0
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61 f04f
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62 f04f
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63 f04f ; CPU initialization
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64 fccc org $FCCC ; Set initialization vectors
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65 fccc 00 f0 word.w INIT
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66 fcce 00 f0 word.w INIT
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