Made use of BIT instruction to access InputFlags from firmware.

Doing the same for access from disk-based software would require selfmodifying code as there's not bit <addr>,x instruction.

Apple2/CommandFirmware.asm

@@ -127,21 +127,14 @@ HelpCommand:
  .byte "a2help",$00
 
 SendByte:
- pha 
-waitWrite: 
- lda InputFlags
- rol
- rol 
- bcs waitWrite
- pla
+ bit InputFlags
+ bvs SendByte
  sta OutputByte
  lda #$1e ; set bit 0 low to indicate write started
  sta OutputFlags 
 finishWrite:
- lda InputFlags
- rol
- rol
- bcc finishWrite
+ bit InputFlags
+ bvc finishWrite
  lda #$1f
  sta OutputFlags
  rts
@@ -150,9 +143,8 @@ GetByte:
  lda #$1d ;set read flag low
  sta OutputFlags
 waitRead:
- lda InputFlags
- rol
- bcc readByte
+ bit InputFlags
+ bpl readByte
  bit Keyboard ;keypress will abort waiting to read
  bpl waitRead
  lda #$1f ;set all flags high and exit
@@ -165,9 +157,8 @@ readByte:
  lda #$1f ;set all flags high
  sta OutputFlags
 finishRead:
- lda InputFlags
- rol
- bcc finishRead
+ bit InputFlags
+ bpl finishRead
  pla
  clc ;success
 end:

Apple2/DriveFirmware.asm

@@ -161,21 +161,14 @@ write256:
  rts
 
 SendByte:
- pha 
-waitWrite: 
- lda InputFlags
- rol
- rol 
- bcs waitWrite
- pla
+ bit InputFlags
+ bvs SendByte
  sta OutputByte
  lda #$0e ; set bit 0 low to indicate write started
  sta OutputFlags
 finishWrite:
- lda InputFlags
- rol
- rol
- bcc finishWrite
+ bit InputFlags
+ bvc finishWrite
  lda #$0f
  sta OutputFlags
  rts
@@ -184,17 +177,15 @@ GetByte:
  lda #$0d ;set read flag low
  sta OutputFlags
 waitRead:
- lda InputFlags
- rol
- bcs waitRead
+ bit InputFlags
+ bmi waitRead
  lda InputByte
  pha
  lda #$0f ;set all flags high
  sta OutputFlags
 finishRead:
- lda InputFlags
- rol
- bcc finishRead
+ bit InputFlags
+ bpl finishRead
  pla
 end:
  rts

Apple2/FileAccessFirmware.asm

@@ -114,21 +114,14 @@ ExitToMonitor:
  jsr Monitor 
 
 SendByte:
- pha 
-waitWrite: 
- lda InputFlags
- rol
- rol 
- bcs waitWrite
- pla
+ bit InputFlags
+ bvs SendByte
  sta OutputByte
  lda #$2e ; set bit 0 low to indicate write started
  sta OutputFlags 
 finishWrite:
- lda InputFlags
- rol
- rol
- bcc finishWrite
+ bit InputFlags
+ bvc finishWrite
  lda #$2f
  sta OutputFlags
  rts
@@ -137,17 +130,15 @@ GetByte:
  lda #$2d ;set read flag low
  sta OutputFlags
 waitRead:
- lda InputFlags
- rol
- bcs waitRead
+ bit InputFlags
+ bmi waitRead
  lda InputByte
  pha
  lda #$2f ;set all flags high
  sta OutputFlags
 finishRead:
- lda InputFlags
- rol
- bcc finishRead
+ bit InputFlags
+ bpl finishRead
  pla
 end:
  rts

Apple2/MenuFirmware.asm

@@ -121,21 +121,14 @@ Boot:
  jmp PageJump
 
 SendByte:
- pha 
-waitWrite: 
- lda InputFlags
- rol
- rol 
- bcs waitWrite
- pla
+ bit InputFlags
+ bvs SendByte
  sta OutputByte
  lda #$3e ; set bit 0 low to indicate write started
  sta OutputFlags 
 finishWrite:
- lda InputFlags
- rol
- rol
- bcc finishWrite
+ bit InputFlags
+ bvc finishWrite
  lda #$3f
  sta OutputFlags
  rts
@@ -144,17 +137,15 @@ GetByte:
  lda #$3d ;set read flag low
  sta OutputFlags
 waitRead:
- lda InputFlags
- rol
- bcs waitRead
+ bit InputFlags
+ bmi waitRead
  lda InputByte
  pha
  lda #$3f ;set all flags high
  sta OutputFlags
 finishRead:
- lda InputFlags
- rol
- bcc finishRead
+ bit InputFlags
+ bpl finishRead
  pla
  rts