From 99394318861405f5417a0ef46410e24adec9f57d Mon Sep 17 00:00:00 2001
From: Leo C <erbl259-lmu@yahoo.de>
Date: Tue, 30 Apr 2019 18:24:42 +0200
Subject: [PATCH] RX/TX int: Improve register allocation. TX int:
 Simplify/optimize flag handling.

---
 cbios/ascii.180 | 82 +++++++++++++++++++++++--------------------------
 1 file changed, 39 insertions(+), 43 deletions(-)

diff --git a/cbios/ascii.180 b/cbios/ascii.180
index e75dd87..2353ae0 100644
--- a/cbios/ascii.180
+++ b/cbios/ascii.180
@@ -591,7 +591,7 @@ asci1_inp:
 	di
 	set	TDC1,(ix+oint.stat)	;
 	in0	a,(stat1)		;
-	or	M_TIE,			;
+	or	M_TIE			;
 	out0	(stat1),a		;
 	ei
 a1i_2:
@@ -673,35 +673,35 @@ asci_int macro	dev
 	local	rxi_2,rxi_3
 
 	push	ix
-rxtxi&dev&_lp0:
 	ld	ix,s&dev&.inbuf		;
+	ld	d,(ix+oint.fflags)
 rxtxi&dev&_lp1:
-	in0	a,(stat&dev)		;receive flag set?
+	in0	e,(stat&dev)		;get asci status
 	jp	p,txi&dev		;RDRF == Bit 7
-	and	M_OVRN+M_PERR+M_FE
-	ld	e,a
 
-	in0	a,(asext&dev)
+	; RX Interrupt
+
+	res	BREAK,e
+	in0	a,(asext&dev)		;get break status
 	and	M_BREAK
-	or	e
+	or	e			;merge to other error flags
 	ld	e,a
 
-	in0	d,(cntla&dev)		;
-	res	EFR,d			;
-	out0	(cntla&dev),d
+	in0	a,(cntla&dev)		;reset all error flags
+	and	~M_EFR			;
+	out0	(cntla&dev),a		;
 
 	ld	c,(ix+o.in_idx)		;input buffer pointer
 	ld	b,0
 	ld	hl,s&dev&.inbuf		;
 	add	hl,bc
 
-	in0	a,(rdr&dev)		;get char
-	ld	(hl),a
+	in0	b,(rdr&dev)		;get char
 					;todo: break detection
-					;todo: parity, framing overrun error
+					;todo: parity, framing, overrun error
+	ld	(hl),b
 
-	ld	e,(ix+oint.fflags)
-;	bit	IXON,e
+;	bit	IXON,d
 ;	jr	z,rxi_2
 					;todo: test XON/XOFF
 rxi_2:
@@ -724,46 +724,42 @@ rxi_2:
 	jr	nz,rxtxi&dev&_lp1
 
    if dev=0				; only channel 0 has rts line
-	bit	CRTS_IFLOW,e
+	bit	CRTS_IFLOW,d
 	jr	z,rxi0_nocrts
 
-	set	EFR,d
-	set	RTS0,d			;RTS inactive
-	out0	(cntla0),d		;
+	in0	a,(cntla&dev)		;reset all error flags
+	or	M_RTS0+M_EFR			;RTS inactive
+	out0	(cntla0),a		;
 rxi0_nocrts:
    endif
 
-	bit	IXOFF,e
+	bit	IXOFF,d
 	jr	z,rxtxi&dev&_lp1
 					;send XOFF
 	set	TDC3,(ix+oint.stat)
-	in0	a,(stat&dev)		;
-	set	TIE,a			;
-	out0	(stat&dev),a		;
+	set	TIE,e			;
+	out0	(stat&dev),e		;
 	jr	rxtxi&dev&_lp1
 
 txi&dev:
-	ld	e,a
 	bit	TDRE,e			;TX int?
 	jr	z,rxtxi&dev&_exit
-					;todo: xon/xoff
-	bit	IXOFF,(ix+oint.fflags)
-	jr	z,txi&dev&_char
-txi&dev&_dc1:
-	bit	TDC1,(ix+oint.stat)
-	jr	z,txi&dev&_dc3
-	res	TDC1,(ix+oint.stat)
-	ld	a,DC1
-	jr	txi&dev&_dc1dc3
-
-txi&dev&_dc3:
-	bit	TDC3,(ix+oint.stat)
-	jr	z,txi&dev&_char
-	res	TDC3,(ix+oint.stat)
-	ld	a,DC3
-txi&dev&_dc1dc3:
-	out0	(tdr&dev),a		;
-	jp	rxtxi&dev&_lp0
+
+	; TX Interrupt
+
+	ld	a,(ix+oint.stat)	;check if xon/xoff should be sent
+	tst	M_TDC1+M_TDC3		;
+	jr	z,txi&dev&_char		;  no
+
+	ld 	l,DC3			;prepare for xoff
+	bit	TDC1,a			;request for xon (also) set?
+	jr	z,txi&dev&_cch		;
+	ld	l,DC1	                ;
+txi&dev&_cch:
+	out0	(tdr&dev),l		;
+	and	~(M_TDC1+M_TDC3)	;reset request flags
+	ld	(ix+oint.stat),a	;
+	jp	rxtxi&dev&_lp1		;
 
 txi&dev&_char:
 	ld	hl,s&dev&.outbuf+o.in_idx	;[in]
@@ -782,7 +778,7 @@ txi&dev&_char:
 	and	c			;
 	ld	(s&dev&.outbuf+o.out_idx),a	;
 
-	jp	rxtxi&dev&_lp0
+	jp	rxtxi&dev&_lp1
 
 txi&dev&_empty:
 	res	TIE,e			;disable tx-int
-- 
2.39.2