Last Updated or created 2022-08-23
UPDATE: 20220823 Sid working
Above is my Kicad design (reverse engineering print below, which was made for my 6802CPU, which i could use to test the 6822 PIA)
The 6822 is simular to 6502 in design. So i’m going to redo this for my 6502.
The 7 segment displays are a start of hex-keyboard/display combo i’m going to post more of in the next days.
Below a part of the rom for the LCD dual line display.
Started to write routines which i can call to manipulate the display. Setting the pointer to a message, setting the line to use and a subset of controlls like: Center, Right, binary to ascii, scrolling, etcetera
lda #0 ; set line number sta lineno ; store jsr gotoline ; goto line in display lda #<message ; get address from message and store for printline subroutine sta messagestore lda #>message sta messagestore+1 jsr printline ; print lda #1 ; set line number sta lineno ; store jsr gotoline lda #<message2 sta messagestore lda #>message2 sta messagestore+1 jsr printline
New address decoder
Below left the new graphical display, below right a test board which shows address lines and decoded chip-enable lines.
A15 high -> ROM
A15 && A14 low -> RAM
combination of A15 low and A14 high – A13 and A12 wil select peripherals.
Above is a start of a wirewrapped version, i also started a PCB design in KIcad that will continuously be changed as i alter designs.
UPDATE SID Working! Using new address decoder.
SID = $7000 makesound: lda #0 sta SID+$5 ; Channel1 - attack/decay lda #250 sta SID+$6 ; Channel1 - Sustain/Release lda #$95 sta SID+$0 ; Channel1 - Frequency low-byte lda #$44 sta SID+$1 ; Channel1 - Frequency high-byte lda #%00100001 sta SID+$4 ; SAW + Gate lda #$0f sta SID+$18 ; Volume max