fixes for IEC

c64/kernal/iec_pull_data_release_atn_clock.s

@@ -0,0 +1,7 @@
+
+iec_pull_data_release_atn_clock:
+	lda CI2PRA
+	ora #BIT_CI2PRA_DAT_OUT                              ; pull
+	and #$FF - BIT_CI2PRA_ATN_OUT - BIT_CI2PRA_CLK_OUT   ; release
+	sta CI2PRA
+	rts

c64/kernal/iec_rx_byte.s

@@ -1,118 +1,103 @@
 	;; Receive a byte from the IEC bus.
-	;; reference http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
+	;; Implemented based on https://www.pagetable.com/?p=1135, https://github.com/mist64/cbmbus_doc,
-	;; page 11.
+	;; http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf (page 11)
-
-
-;; XXX rework this, according to pagetable.com
 
 iec_rx_byte:
 
+	;; First, we wait for the talker to release the CLK line
+	jsr iec_wait_for_clk_release
+
+	;; We then release the DATA to signal we are ready
+	;; We can use this routine, since we weren't pulling CLK anyway
+	jsr iec_release_clk_data
+
+	;; Wait for talker to pull CLK.
+	;; If over 200 usec (205 cycles on NTSC machine) , then it is EOI.
+	;; Loop iteraction takes 13 cycles, 17 full iterations are enough
+
+	ldx #$11                  ; 2 cycles
+iec_rx_clk_wait:
+	lda CI2PRA                ; 4 cycles
+	rol                       ; 2 cycles, to put BIT_CI2PRA_CLK_IN as the last bit
+	bpl iec_rx_not_eoi        ; 2 cycles if not jumped
+	dex                       ; 2 cycles
+    bne iec_rx_clk_wait       ; 3 cycles if jumped
+    
+	;; Timeout - wait for pulled CLK and pull data for 60 usec to confirm
+	jsr iec_wait_for_clk_pull
+	jsr iec_release_clk_pull_data
+	jsr iec_wait60us
+	jsr iec_release_clk_data
+
+	;; Store EOI information in IOSTATUS - XXX this should be done by the caller!
+	lda IOSTATUS
+	ora #$40
+	sta IOSTATUS
+	
+	sec
 	rts
 
-;	;; First, we wait for the talker to release the CLK line.
+iec_rx_not_eoi:
-;	;; XXX jsr iec_wait_for_clock_release
 
-;	;; We then release the data line
+	;; Latch input bits in on rising edge of CLK, eight times for eight bits.
-;	;; (We can use this routine, since we weren't holding CLK, anyway)
+	ldx #7
-;	jsr iec_release_clk_and_data
 
-;	;; Wait for talker to assert CLK.
+	;; Get empty byte to load into.
-;	;; If >200usec, then it is EOI and we have to assert the
+	lda #$00
-;	;; DATA line for 60 usec to tell the TALKER that we have
+	pha
-;	;; acknowledged the EOI.
-;	ldx #20
-iec_rx_clk_wait:
-;	;; Loop takes 11 usec, so ~20 iterations for 200usec timeout
-;	lda $dd00
-;	rol
-;	bpl not_eoi
-;	dex
-;	cpx #$21
-;	bne not_rx_timeout
-;	;; Time out waiting for CLK to assert again.
-;	;;  = error
-;	sec
-;	rts
-not_rx_timeout:
-;	cpx #$00
-;	bpl iec_rx_clk_wait
-
-;	;; Remember EOI condition
-;	lda IOSTATUS
-;	ora #$40
-;	sta IOSTATUS
-
-;	;; EOI timeout: So pulse DATA line for 60 usec
-;	jsr iec_assert_data
-;	jsr iec_wait60us
-;	jsr iec_release_clk_and_data
-
-;	;; And still wait for CLK to be asserted
-;	;; XXX - This will cause periodic EOI pulses if the sender takes too long.
-;	;; That is probably ok.
-;	ldx #$7f
-;	jmp iec_rx_clk_wait
-
-not_eoi:
-;	;; CLK is now low.  Latch input bits in on rising edge
-;	;; of CLK, eight times for eight bits.
-;	ldx #7
-
-;	;; Get empty byte to load into.
-;	lda #$00
-;	pha
 
 iec_rx_bit_loop:
 
-;	;; Wait for CLK to release
+	;; Wait for CLK to release
-;	;; jsr iec_wait_for_clock_release
+	jsr iec_wait_for_clk_release
-;	;; (we do this implicitly below, with a tighter routine,
-;	;; so that we don't have timing problems, as the requirements
-;	;; are quite tight. Basically we need to read the clock and data
-;	;; bit from the same byte read.
 
-;	;; DATA now has the next bit, but inverted (well, except that it turns out not to be).
+	;; (we do this implicitly below, with a tighter routine,
-;	;; DATA is in bit7, which is a bit annoying.
+	;; so that we don't have timing problems, as the requirements
-;	;; But we can clock it out with a ROL instruction
+	;; are quite tight. Basically we need to read the clock and data
-;	;; so that it is in C. We can then ROR it into the
+	;; bit from the same byte read.
-;	;; partial data byte.
-;	;; We use ROR so that we shift in from the top, so that
-;	;; the first bit we shift in ends up in bit 0 after all
-;	;; 8 bits have been read.
-;	;; ODD: For some reason we don't need to invert the
-;	;; received bits.  This is weird, because we invert them
-;	;; on the way out, and everything in the protocol seems
-;	;; to indicate that we sould do so.  But experimentation
-;	;; has confirmed the bits don't need inversion on reception.
 
-;	;; Move data bit into C flag, and loop until bit 6 clears
+	;; DATA now has the next bit, but inverted (well, except that it turns out not to be).
-;	;; i.e., the clock has been released.
+	;; DATA is in bit 7, which is a bit annoying.
-;*	LDA $DD00
+	;; But we can clock it out with a ROL instruction
-;	ROL
+	;; so that it is in C. We can then ROR it into the
-;	bpl -
+	;; partial data byte.
+	;; We use ROR so that we shift in from the top, so that
+	;; the first bit we shift in ends up in bit 0 after all
+	;; 8 bits have been read.
+	;; ODD: For some reason we don't need to invert the
+	;; received bits.  This is weird, because we invert them
+	;; on the way out, and everything in the protocol seems
+	;; to indicate that we sould do so.  But experimentation
+	;; has confirmed the bits don't need inversion on reception.
 
-;	;; Pull it into the data byte
+	;; Move data bit into C flag, and loop until bit 6 clears
-;;	pla
+	;; i.e., the clock has been released.
-;	ROR
+*	lda CI2PRA
-;	pha
+	rol
+	bpl -
 
-;	;; Wait for CLK to re-assert
+	;; Pull it into the data byte
-;	jsr iec_wait_for_clock_assert
+	pla
+	ror
+	pha
 
-;	;; More bits?
+	;; Wait for CLK to be pulled again
-;	dex
+	jsr iec_wait_for_clk_pull
-;	bpl iec_rx_bit_loop
 
-;	;; Then we must within 1000usec acknowledge the frame by
+	;; More bits?
-;	;; asserting DATA. At this point, CLK is asserted by the
+	dex
-;	;; talker and DATA by us, i.e., we are ready to receive
+	bpl iec_rx_bit_loop
-;	;; the next byte. (p11).
-;	jsr iec_assert_data
 
-;	;; Retreive the received byte
+	;; Then we must within 1000 usec acknowledge the frame by
-;	PLA
+	;; pulling DATA. At this point, CLK is pulled by the
+	;; talker and DATA by us, i.e., we are ready to receive
+	;; the next byte. (p11).
+	jsr iec_release_clk_pull_data
 
-;	;; Return no-error
+	;; Retreive the received byte
-;	CLC
+	pla
-;	RTS
+
+	;; Return no-error
+	clc
+	rts
 

c64/kernal/iec_turnaround_to_listen.s

@@ -1,39 +1,29 @@
 	;; 	According to http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
 	;;  	pages 7--8.
-	
+	;; See also https://www.pagetable.com/?p=1135, https://github.com/mist64/cbmbus_doc
+
 iec_turnaround_to_listen:
 
-	;; Assert data and release clock
+	;; Pull DATA, release CLK and ATN (we are not sending commands)
-	lda $dd00
+	jsr iec_pull_data_release_atn_clock
-	and #$ef		; release clock (bit 4)
+
-	ora #$20     		; assert data (bit 5)
+	;; Wait for clock line to be pulled by the drive
-	sta $dd00
+	ldx #$FF ; XXX should we really use that high number?
-	
+*
-	;; Wait for clock line to be asserted by the drive
+	lda CI2PRA
-*	lda $dd00
+	rol    ; to put BIT_CI2PRA_CLK_IN as the last (sign) bit 
-	and #$40
+	bpl +
+	dex
 	bne -
 
-	;; http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
+	;; Timeout
-	;; page 8 tells us we should not do anything here after waiting for
+	jsr printf
-	;; the clock line to assert.
+	.byte "DBG: TURNAROUND FAILED",$0d,$00
-	
+	sec
- 	ldx #$ff
+	rts
- *	lda $dd00
- 	and #$40
- 	bne +
- 	dex
- 	bne -
 
-	 ;; jsr printf
+	;; CLK is pulled by the device, OK
-	 ;; .byte "TURNAROUND FAILED - FILE NOT FOUND?",$0d,$00
+*	
-	
-	;; ;; Timeout = file not found error
-	;; ;; (https://www.pagetable.com/?p=1023)
-	 lda #4
-	 sec
-	 rts
-*
-	;; ATN turn around successful
 	clc
 	rts
+

c64/kernal/iec_tx_command.s

@@ -35,7 +35,7 @@ iec_tx_command:
 
 	;; Common part of iec_txbyte and iec_tx_common - waits for devices
 	;; and transmits a byte
-	
+
 	pla
 	jsr iec_tx_common
 

c64/kernal/iec_tx_common.s

@@ -6,11 +6,12 @@ iec_tx_common:
 
 	;; Store the bye to send on a stack
 	pha
-
+	
 	;; Wait till all receivers are ready, they should all release DATA
 	jsr iec_wait_for_data_release
-	
+
 	;; Pull CLK back to indicate that DATA is not valid, keep it for 60us
+	;; We can use this routine as we don't hold DATA anyway (and its state doesn't even matter)
 	;; Don't wait too long, as 200us or more is considered EOI
 
 	jsr iec_pull_clk_release_data
@@ -42,11 +43,14 @@ iec_tx_common_bit_is_sent:
 	pla
 	dex
 	bpl iec_tx_common_nextbit
-	
+
+	;; Whole byte send, make sure ATN is released
+	jsr iec_release_atn_clk_data
+
 	;; XXX the flow below is REALLY dangerous, as if there are multiple devices,
 	;; one can signal that it's busy much earlier (more than 100ms) than the other.
 	;; Can we do something about it?
-
+	
 	;; All done - give devices time to tell if they are busy by pulling DATA
 	;; They should do it within 1ms
 	ldx #$FF
@@ -62,7 +66,9 @@ iec_tx_common_bit_is_sent:
 	jsr iec_wait100us
 	
 iec_tx_common_done:
+
 	;; Byte sent, return
+	clc
 	rts
 	
 iec_tx_common_nextbit:

c64/kernal/iec_tx_eoi.s

@@ -1,9 +1,10 @@
 
 iec_tx_eoi:
 
-	;; Wait at least 200us
+	;; Wait at least 256 usec
 	jsr iec_wait100us
 	jsr iec_wait100us
+	jsr iec_wait60us
 
 	;; Restore the bus to idle state
 	jsr iec_set_idle

c64/kernal/iec_wait100us.s

@@ -4,9 +4,9 @@ iec_wait100us:
 	;; Wait 100usec
 
 	;; PAL:
-	;; - CPU frequency 0.985248 MHz, we need to waste at least 102 cycles
+	;; - CPU frequency 0.985248 MHz, we need to waste at least  99 cycles
 	;; NTSC:
-	;; - CPU frequency 1.022727 MHZ, we need to waste at least 98 cycles
+	;; - CPU frequency 1.022727 MHZ, we need to waste at least 103 cycles
 
 	;; Waste cycles by reading some unimportant memory location
 	;; (in a loop) in order not to clutter VICE debug logs

c64/kernal/iec_wait20us.s

@@ -4,9 +4,9 @@ iec_wait20us:
 	;; Wait 20usec
 
 	;; PAL:
-	;; - CPU frequency 0.985248 MHz, we need to waste at least 21 cycles
+	;; - CPU frequency 0.985248 MHz, we need to waste at least 20 cycles
 	;; NTSC:
-	;; - CPU frequency 1.022727 MHZ, we need to waste at least 20 cycles
+	;; - CPU frequency 1.022727 MHZ, we need to waste at least 21 cycles
 
 	;; Waste cycles by reading some unimportant memory location
 	;; in order not to clutter VICE debug logs

c64/kernal/iec_wait60us.s

@@ -4,9 +4,9 @@ iec_wait60us:
 	;; Wait 60usec
 
 	;; PAL:
-	;; - CPU frequency 0.985248 MHz, we need to waste at least 61 cycles
+	;; - CPU frequency 0.985248 MHz, we need to waste at least 60 cycles
 	;; NTSC:
-	;; - CPU frequency 1.022727 MHZ, we need to waste at least 59 cycles
+	;; - CPU frequency 1.022727 MHZ, we need to waste at least 62 cycles
 
 	;; Waste cycles in a loop
 

c64/kernal/iec_wait_for_clk_pull.s

@@ -0,0 +1,6 @@
+
+iec_wait_for_clk_pull:
+	lda CI2PRA
+	rol    ; to put BIT_CI2PRA_CLK_IN as the last (sign) bit 
+	bmi iec_wait_for_clk_pull
+	rts

c64/kernal/iec_wait_for_clk_release.s

@@ -0,0 +1,6 @@
+
+iec_wait_for_clk_release:
+	lda CI2PRA
+	and #BIT_CI2PRA_CLK_IN
+	beq iec_wait_for_clk_release
+	rts

c64/kernal/open.s

@@ -15,9 +15,6 @@ open:
 	bcs +
 	bmi open_has_space
 *
-	jsr printf
-	.byte "FULL", $0D, 0
-
 	;; Table is full - according to https://codebase64.org/doku.php?id=base:kernalreference
 	;; C flag set means error occured
 	sec
@@ -74,11 +71,9 @@ open_rs232:
 
 open_iec:
 
-	;; XXX add FILENAM support, test it
+	;; Part implemented according to https://www.pagetable.com/?p=1031, https://github.com/mist64/cbmbus_doc
 
-	;; Sequence is:
+	;; XXX for now for channel 15 only!
-	;; 1. Call current device to attention as LISTENER = $20 + device
-	;; 2. 
 
 	;; Disable IRQs, since timing matters!
 	sei
@@ -86,14 +81,25 @@ open_iec:
 	;; Begin sending under attention
 	;; XXX jsr iec_assert_atn
 
-	;; CLK is now asserted, and we are ready to transmit a byte
+	;; Request device to talk
 	lda current_device_number
-	jsr listen
+	jsr talk
-	bcs open_iec_error
+	bcs open_iec_error ; XXX what about the accumulator?
+
+	jsr printf
+	.byte "DBG: OPEN 1", $0D, 0
+	
+	;; Send secondary address
+	lda current_secondary_address
+	jsr tksa
+	bcs open_iec_error ; XXX what about the accumulator?
+
+	jsr printf
+	.byte "DBG: OPEN 2", $0D, 0
 
 	;; Indicate success
 	lda #$00
-	clc	
+	clc
 
 open_iec_error:
 	;; Re-enable interrupts and return

c64/kernal/tksa.s

@@ -1,3 +1,12 @@
 ; Function defined on pp272-273 of C64 Programmers Reference Guide
 tksa:
+
+	;; This routine is documented in 'C64 Programmer's Reference Guide', page 302 and
+	;; https://www.pagetable.com/?p=1031, , https://github.com/mist64/cbmbus_doc
+	ora #$F0
+	jsr iec_tx_command
+	bcs tksa_error
+	jmp iec_turnaround_to_listen
+	
+tksa_error:
 	rts