IEC cleanups and size optimization

c64/kernal/f34a.open.s

@@ -76,7 +76,7 @@ open_iec:
 	lda current_secondary_address
 	jsr iec_cmd_open
 	bcc +
-	jmp kernalerror_DEVICE_NOT_FOUND ; XXX find a better error message for wrong channel (create new one?)
+	jmp kernalerror_DEVICE_NOT_FOUND
 *
 
 	;; We need our helpers to get to filenames under ROMs or IO area

c64/kernal/f4a5.load.s

@@ -65,7 +65,7 @@ load:
 	;; Open channel 0 (reserved for file reading)
 	lda #$00
 	jsr iec_cmd_open
-	bcs lvs_load_verify_error
+	bcs lvs_device_not_found_error
 
 	;; Send file name
 	jsr lvs_send_file_name

c64/kernal/iec/iec_tx_byte.s

@@ -19,11 +19,73 @@ iec_tx_byte:
 	;; and it is going to be a data byte (released ATN)
 	jsr iec_release_atn_clk_data
 
-	;; Common part of iec_txbyte and iec_tx_common - waits for devices
+	;; Common part of iec_tx_byte and iec_tx_command
-	;; and transmits a byte
+	;; Implemented based on https://www.pagetable.com/?p=1135, https://github.com/mist64/cbmbus_doc
+	;; and http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
+
+iec_tx_common:
+
+	;; Timing is critical here - execute on disabled IRQs
+	php
+	sei
+
+	;; Wait till all receivers are ready, they should all release DATA
+	jsr iec_wait_for_data_release
+
+	;; At this point a delay 256 usec or more is considered EOI - add waits if necessary
+	bcc +
+	jsr iec_wait100us
+	jsr iec_wait100us
+	jsr iec_wait60us
+
+	;; XXX waits above should be enough - why do we need more waits???
+	jsr iec_wait100us
+	jsr iec_wait100us
+	jsr iec_wait100us
+
+	;; Receiver should now acknowledge EOI by pulling data for at least 60 usec
+	jsr iec_wait60us
+	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)
+
+	jsr iec_pull_clk_release_data_oneshot
+	jsr iec_wait60us
+
+	;; Now, we can start transmission of 8 bits of data
+	ldx #7
+
+iec_tx_common_sendbit:
+	;; Is next bit 0 or 1?
+	lda IEC_TMP2
+	lsr
+	sta IEC_TMP2
+	bcs +
+
+	;; Bit is 0
+	jsr iec_release_clk_pull_data
+	jmp iec_tx_common_bit_is_sent
+*
+	;; Bit is 1
+	jsr iec_release_clk_data
+
+iec_tx_common_bit_is_sent:
+
+	;; Wait 20us, so that device(s) can pick DATA
+	jsr iec_wait20us
+
+	;; Pull CLK for 20us again, before sending the next bit
+	;; or performing any other action
+	jsr iec_pull_clk_release_data_oneshot
+	jsr iec_wait20us
+
+	;; More bits to send?
+	dex
+	bpl iec_tx_common_sendbit
+
+	plp
 
-	jsr iec_tx_common
-	
 	;; Give device time to tell if they are busy by pulling DATA
 	;; They should do it within 1ms
 	ldx #$FF
@@ -36,5 +98,3 @@ iec_tx_byte:
 	bpl iec_return_DEVICE_NOT_FOUND
 *
 	jmp iec_return_success
-
-

c64/kernal/iec/iec_tx_command.s

@@ -20,8 +20,9 @@ iec_tx_command:
 	jsr iec_pull_atn_clk_release_data
 
 	;; Give devices time to respond (response is mandatory!) by pulling DATA
-	jsr iec_wait1ms_for_data
+	jsr iec_wait1ms
-	bmi iec_tx_command_dev_not_found
+	lda CIA2_PRA ; pulled DATA = highest bit 0 = 'plus'
+	bmi iec_return_DEVICE_NOT_FOUND
 
 	;; At least one device responded, but they are still allowed to stall
 	;; (can be busy processing something), we have to wait till they are all
@@ -34,19 +35,5 @@ iec_tx_command:
 	;; and transmits a byte
 
 	clc ; Carry flag set is used for EOI mark
-	jsr iec_tx_common
+	jmp iec_tx_common
 
-	;; According to https://www.pagetable.com/?p=1135 there is some complicated and dangerous
-	;; flow here, but http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf (page 6)
-	;; advices to just wait 1ms and check the DATA status
-
-	jsr iec_wait1ms_for_data
-	bmi iec_tx_command_dev_not_found
-
-	;; Done
-
-	jmp iec_return_success
-
-iec_tx_command_dev_not_found:
-
-	jmp iec_return_DEVICE_NOT_FOUND

c64/kernal/iec/iec_tx_common.s

@@ -1,72 +0,0 @@
-
-;; This is a common part of iec_tx_byte and iec_tx_command
-;; Implemented based on https://www.pagetable.com/?p=1135, https://github.com/mist64/cbmbus_doc
-;; and http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
-
-;; Expects byte to send in IEC_TMP2 ($A4 is a byte buffer according to http://sta.c64.org/cbm64mem.html)
-;; Carry flag set = signal EOI
-
-iec_tx_common:
-
-	;; Timing is critical here - execute on disabled IRQs
-	php
-	sei
-
-	;; Wait till all receivers are ready, they should all release DATA
-	jsr iec_wait_for_data_release
-
-	;; At this point a delay 256 usec or more is considered EOI - add waits if necessary
-	bcc +
-	jsr iec_wait100us
-	jsr iec_wait100us
-	jsr iec_wait60us
-
-	;; XXX waits above should be enough - why do we need more waits???
-	jsr iec_wait100us
-	jsr iec_wait100us
-	jsr iec_wait100us
-
-	;; Receiver should now acknowledge EOI by pulling data for at least 60 usec
-	jsr iec_wait60us
-	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)
-
-	jsr iec_pull_clk_release_data_oneshot
-	jsr iec_wait60us
-
-	;; Now, we can start transmission of 8 bits of data
-	ldx #7
-
-iec_tx_common_sendbit:
-	;; Is next bit 0 or 1?
-	lda IEC_TMP2
-	lsr
-	sta IEC_TMP2
-	bcs +
-
-	;; Bit is 0
-	jsr iec_release_clk_pull_data
-	jmp iec_tx_common_bit_is_sent
-*
-	;; Bit is 1
-	jsr iec_release_clk_data
-	
-iec_tx_common_bit_is_sent:
-
-	;; Wait 20us, so that device(s) can pick DATA
-	jsr iec_wait20us
-
-	;; Pull CLK for 20us again, before sending the next bit
-	;; or performing any other action
-	jsr iec_pull_clk_release_data_oneshot
-	jsr iec_wait20us
-
-	;; More bits to send?
-	dex
-	bpl iec_tx_common_sendbit
-
-	plp
-	rts ; Flow continues differently for data/command
-

c64/kernal/iec/iec_wait1ms.s

@@ -1,6 +1,6 @@
 
 ;;
-;; Wait 1 ms (1000 usec) - afterwards can use 'bpl' to check that DATA is pulled
+;; Wait 1 ms (1000 usec)
 ;;
 ;; On NTSC this means 1023 cycles (slightly less on PAL, but we have to be sure).
 ;; We can't count on badlines, as the screen might be disabled.
@@ -8,7 +8,7 @@
 ;; 63 cycles, we need at least 17 full rasters to be 100% sure we wait enough
 
 
-iec_wait1ms_for_data:
+iec_wait1ms:
 	ldx #18 ; we probably won't start with the beginning of raster
 	lda VIC_RASTER
 *
@@ -18,5 +18,4 @@ iec_wait1ms_for_data:
 	dex
 	bne -
 
-	lda CIA2_PRA ; pulled DATA = highest bit 0 = 'plus'
 	rts