From c40499b83f238de9b1a88a080261546149784586 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Thu, 3 Dec 2020 19:03:08 +0100
Subject: some more opcodes for delay 7-seg example

---
 roms/7seg_print_loop_delay.asm     | 90 ++++++++++++++++++++++++++++++++++++++
 roms/7seg_print_one_subroutine.asm |  6 +--
 2 files changed, 93 insertions(+), 3 deletions(-)
 create mode 100644 roms/7seg_print_loop_delay.asm

(limited to 'roms')

diff --git a/roms/7seg_print_loop_delay.asm b/roms/7seg_print_loop_delay.asm
new file mode 100644
index 0000000..82ec4db
--- /dev/null
+++ b/roms/7seg_print_loop_delay.asm
@@ -0,0 +1,90 @@
+PORTA = $6001
+DDRA  = $6003
+ 
+SER   = %00000001
+RCLK  = %00000010
+SRCLK = %00000100
+
+COUNTER = $0
+
+ .org #$f800
+
+reset:  
+ ldx #$FF			; initialize call stack to $1FF
+ txs
+
+ ldx #%00000111			; set output on 7seg control pins of PORTA
+ stx DDRA
+ 
+ ldx #$0			; initialize 8-bit counter
+ stx COUNTER
+ 
+mainloop:			; main loop, load counter and print it
+ jsr print7seg
+ ldx #0				; ca 500'000 cycles, at 1 Mhz 2 ticks per second
+ ldy #0
+ lda #150
+ jsr delay
+ inc COUNTER
+ lda COUNTER
+ jmp mainloop
+ 
+print7seg:
+ ldy #$8			; 8 bits to shift
+loop7seg:
+ rol a
+ bcc zerobit			; C=0, bang a zero to SER
+onebit:
+ ldx #(SER)			; C=1, bang a one to SER
+ stx PORTA
+ ldx #(SER | SRCLK)
+ stx PORTA
+ ldx #(SER)
+ stx PORTA
+ jmp next
+zerobit:
+ ldx #$0			; C=0, bang a zero to SER
+ stx PORTA
+ ldx #SRCLK
+ stx PORTA
+ ldx #$0
+ stx PORTA
+ jmp next
+next:
+ dey
+ bne loop7seg
+ rol a				; restore A register
+output:
+ ldx #0				; bang RCLK to store output in latch
+ stx PORTA
+ ldx #RCLK
+ stx PORTA
+ ldx #0
+ stx PORTA
+ rts
+
+; delay 18+13(65536Y+256A+X) cycles
+delay:
+ iny
+delay1:
+ nop
+ nop
+delay2:
+ cpx #$1
+ dex
+ sbc #$0
+ bcs delay1
+ dey
+ bne delay2
+ rts
+  
+nmi:
+ rti
+
+irq:
+ rti
+
+ .org #$fffa
+ .word nmi
+ .word reset
+ .word irq
diff --git a/roms/7seg_print_one_subroutine.asm b/roms/7seg_print_one_subroutine.asm
index 4a1839f..2310e02 100644
--- a/roms/7seg_print_one_subroutine.asm
+++ b/roms/7seg_print_one_subroutine.asm
@@ -17,6 +17,9 @@ reset:
  lda #$a5			; 10100101, data to show
  jsr print7seg
 
+term:
+ jmp term
+
 print7seg:
  ldy #$8			; 8 bits to shift
 loop:
@@ -51,9 +54,6 @@ output:
  stx PORTA
  rts
   
-term:
- jmp term
-
 nmi:
  rti
 
-- 
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