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Serial: Optimize SER_IRQ

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Apple2 and Atmos have Index in X, but can still use it for the
best-case path as long as we reload it in the worst-case part
(when we assert flow control).
Also, standardize the free space to trigger flow control to 32
characters left (compare with RecvFreeCnt before decrement)
This commit is contained in:
Colin Leroy-Mira 2023-08-30 21:14:07 +02:00
parent 3f3b6123b9
commit 89af42e5cb
2 changed files with 8 additions and 8 deletions
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8
libsrc/apple2/ser/a2.ssc.s
View File

@ -404,19 +404,19 @@ SER_IRQ:
and #$08
beq Done ; Jump if no ACIA interrupt
lda ACIA_DATA,x ; Get byte from ACIA
ldy RecvFreeCnt ; Check if we have free space left
ldx RecvFreeCnt ; Check if we have free space left
beq Flow ; Jump if no space in receive buffer
ldy RecvTail ; Load buffer pointer
sta RecvBuf,y ; Store received byte in buffer
inc RecvTail ; Increment buffer pointer
dec RecvFreeCnt ; Decrement free space counter
ldy RecvFreeCnt ; Check for buffer space low
cpy #33
cpx #33 ; Check for buffer space low
bcc Flow ; Assert flow control if buffer space low
rts ; Interrupt handled (carry already set)
; Assert flow control if buffer space too low
Flow: lda RtsOff
Flow: ldx Index
lda RtsOff
sta ACIA_CMD,x
sta Stopped
sec ; Interrupt handled

8
libsrc/atmos/ser/atmos-acia.s
View File

@ -329,19 +329,19 @@ SER_IRQ:
and #$08
beq Done ; Jump if no ACIA interrupt
lda ACIA::DATA,x ; Get byte from ACIA
ldy RecvFreeCnt ; Check if we have free space left
ldx RecvFreeCnt ; Check if we have free space left
beq Flow ; Jump if no space in receive buffer
ldy RecvTail ; Load buffer pointer
sta RecvBuf,y ; Store received byte in buffer
inc RecvTail ; Increment buffer pointer
dec RecvFreeCnt ; Decrement free space counter
ldy RecvFreeCnt ; Check for buffer space low
cpy #33
cpx #33
bcc Flow ; Assert flow control if buffer space low
rts ; Interrupt handled (carry already set)
; Assert flow control if buffer space too low
Flow: lda RtsOff
Flow: ldx Index ; Reload port
lda RtsOff
sta ACIA::CMD,x
sta Stopped
sec ; Interrupt handled