refactored LOAD routine so that it's parts are reuseable

c64/aliases/,aliases_ram_lowmem.s

@@ -1,33 +1,92 @@
 ;;
-;; Names of ZP and low memory locations (only the implemented ones)
+;; Names of ZP and low memory locations
 ;; (https://www.c64-wiki.com/wiki/Zeropage)
 ;;
 
-	;; $000-$001 - 6502 CPU registers
+	;; $00-$01 - 6502 CPU registers are here
+
+    ;;
+	;; Page 0 - BASIC area ($02-$8F)
+    ;;
+	
+	.alias TXTTAB     $2B
+
+    ;;
+	;; Page 0 - Kernal area ($90-$FF)
+    ;;
+	
+	.alias IOSTATUS   $90
+	.alias STKEY      $91 ; Keys down clears bits. STOP - bit 7, C= - bit 6, SPACE - bit 4, CTRL - bit 2
+	
+	.alias VERCK      $93 ; 0 = LOAD, 1 = VERIVY
+	
+	.alias C3PO       $94 ; flag - is BSOUR content valid
+	.alias BSOUR      $95 ; serial bus buffered output byte
+
+	.alias LDTND      $98 ; number of entries in LAT / FAT / SAT tables
+	.alias DFLTN      $99
+	.alias DFLTO      $9A
+	
+	.alias MSGFLG     $9D ; bit 6 = error messages, bit 7 = control message
+
+	.alias TIME       $A0 ; $A0-$A2, jiffy clock
+
+	;; 2-byte location below seems to be a good place for temporary storage,
+	;; it seems used for timing during tape reads only - see:
+	;; - 'C64 Programmer's Reference Guide', page 314
+	;; - 'Compute's Mapping the Commodore 64', page 32
+	.alias CMP0       $B0 ; $B0-$B1
+	
+	.alias FNLEN      $B7 ; current file name length
+	
+	.alias STAL       $C1 ; $C1-$C2 LOAD/SAVE start address
+
+    ;;
+	;; Other low memory addresses
+    ;;
+	
+	;; Kernal tables for opened files, 10 entries each
+	.alias LAT        $259 ; logical file numbers
+	.alias FAT        $263 ; device numbers
+	.alias SAT        $26D ; secondary addresses
+
+	.alias MEMSTR     $281
+	.alias MEMSIZ     $283 ; NOTE: Mapping the 64 erroniously has the hex as $282, while the DEC is correct
+
+	.alias HIBASE     $288 ; high byte of start of screen
+
+	.alias RSSTAT     $297 ; RS-232 status
+
+	.alias PALNTSC    $2A6 ; 0 = NTSC, 1 = PAL
+	
 	
 	;; Registers for SYS call
-	.alias sys_reg_a $30c
+	.alias SAREG      $30C
-	.alias sys_reg_x $30d
+	.alias SXREG      $30D
-	.alias sys_reg_y $30e
+	.alias SYREG      $30E
-	.alias sys_reg_p $30f
+	.alias SPREG      $30F
-	.alias sys_jmp   $310
+
+	.alias USRPOK     $310 ; JMP instruction
+	.alias USRADD     $311 ; $311 - $312
 	
 	;; Kernal vectors - interrupts
-	.alias CINV      $0314
+	.alias CINV       $314
-	.alias CBINV     $0316 
+	.alias CBINV      $316 
-	.alias NMINV     $0318
+	.alias NMINV      $318
 	
 	;; Kernal vectors - routines
-	.alias IOPEN     $031A
+	.alias IOPEN      $31A
-	.alias ICLOSE    $031C
+	.alias ICLOSE     $31C
-	.alias ICHKIN    $031E
+	.alias ICHKIN     $31E
-	.alias ICKOUT    $0320
+	.alias ICKOUT     $320
-	.alias ICLRCH    $0322
+	.alias ICLRCH     $322
-	.alias IBASIN    $0324
+	.alias IBASIN     $324
-	.alias IBASOUT   $0326
+	.alias IBASOUT    $326
-	.alias ISTOP     $0328
+	.alias ISTOP      $328
-	.alias IGETIN    $032A
+	.alias IGETIN     $32A
-	.alias ICLALL    $032C
+	.alias ICLALL     $32C
-	.alias USRCMD    $032E
+	.alias USRCMD     $32E
-	.alias ILOAD     $0330
+	.alias ILOAD      $330
-	.alias ISAVE     $0331
+	.alias ISAVE      $331
+
+	.alias TBUFFR     $33C ; $33C-$3FB, tape buffer	

c64/basic/,aliases.s

@@ -52,33 +52,13 @@
 	.alias memmove_dst $6b
 	.alias memmove_size $6d	
 	
-	.alias TXTTAB $2B
-	.alias IOSTATUS $90
-	; Keys down clears bits. STOP=bit 7, C= bit 6, SPACE bit 4, CTRL bit 2
-	.alias BUCKYSTATUS $91
-	.alias load_or_verify_flag $93
-	.alias C3PO  $94 ; flag - is BSOUR content valid
-	.alias BSOUR $95 ; serial bus buffered output byte
 	.alias current_file_num $98
-	.alias LDTND $98 ; number of entries in LAT / FAT / SAT tables
-	.alias DFLTN $99
-	.alias input_device_number DFLTN
-	.alias MSGFLG $9D ; bit 6 = error messages, bit 7 = control message
-	.alias jiffy_clock_24bits $a0
 	.alias cassette_buffer_bytes_used $A6
 	.alias load_or_scroll_temp_pointer $AC
 	;; We also use the following for temp colour pointer when scrolling
 	.alias load_save_verify_end_address $AE
 
-	;; 2-byte location below seems to be a good place for temporary storage,
-	;; it seems used for timing during tape reads only - see:
-	;; - 'C64 Programmer's Reference Guide', page 314
-	;; - 'Compute's Mapping the Commodore 64', page 32
-	.alias CMP0 $B0 ;; $B0-$B1
-
-
 	.alias cassette_buffer_ptr $B2
-	.alias current_filename_length $B7
 	.alias current_logical_filenum $B8
 	.alias current_secondary_address $B9
 	.alias current_device_number $BA
@@ -113,18 +93,10 @@
 
 	.alias basic_input_buffer $0200
 		
-	;; Kernal tables for opened files, 10 entries each
-	.alias LAT $0259 ; logical file numbers
-	.alias FAT $0263 ; device numbers
-	.alias SAT $026D ; secondary addresses	
-	
 	; "Compute's Mapping the 64" book
 	.alias keyboard_buffer $0277
-	.alias MEMSTR $0281
-	.alias MEMSIZ $0283 	; NOTE: Mapping the 64 erroniously has the hex as $282, while the DEC is correct
 	.alias text_colour $0286 ; p55
 	.alias colour_under_cursor $0287 ; p56
-	.alias HIBASE $0288     ; p56 (high byte of start of screen)
 	.alias key_buffer_size $0289 ; p57
 
 	;; 0 = cursor keys, insert, delete and space repeat, but nothing else
@@ -140,8 +112,6 @@
 	.alias keyboard_decoding_ptr $028F
 	.alias enable_case_switch $0291
 	.alias screen_scroll_disable $0292
-	.alias RSSTAT $0297 ; RS-232 status
-	.alias pal_or_ntsc $02A6
 
 	;; BASIC uses some extra bytes for memory access under ROMs located at $2A7 onwards
 	;; IRQs are disabled when doing such accesses, and a default NMI handler only increments

c64/basic/basic_execute_line.s

@@ -29,7 +29,7 @@ no_space_to_skip:
 basic_execute_statement:
 
 	;; Check for RUN/STOP
-	lda BUCKYSTATUS
+	lda STKEY
 	bpl basic_do_break
 	
 	;; Skip over any white space and :

c64/basic/cmd_list.s

@@ -22,7 +22,7 @@ list_loop:
 	jmp basic_main_loop
 
 list_more_lines:
-	lda BUCKYSTATUS
+	lda STKEY
 	bmi +
 	jmp basic_do_break
 *

c64/basic/cmd_load.s

@@ -26,7 +26,7 @@ cmd_load:
 
 	;; Set filename and length
 	lda #$00
-	sta current_filename_length
+	sta FNLEN
 
 	;; Without tape support, LOAD must have a filename
 	;; (This also skips any leading spaces)
@@ -57,7 +57,7 @@ getting_filename:
 
 	jmp got_filename
 *
-	inc current_filename_length
+	inc FNLEN
 	jmp getting_filename
 	
 got_filename:	

c64/basic/cmd_sys.s

@@ -10,22 +10,22 @@ cmd_sys:
 	jsr basic_parse_line_number
 
 	;; setup call
-	lda #$4c 		;JMP
+	lda #$4C ;JMP
-	sta sys_jmp
+	sta USRPOK
 	lda basic_line_number+0
-	sta sys_jmp+1
+	sta USRADD+0
 	lda basic_line_number+1
-	sta sys_jmp+2
+	sta USRADD+1
 	
 	;; Setup the register values
-	lda sys_reg_p
+	lda SPREG
 	pha
-	ldy sys_reg_y
+	ldy SYREG
-	ldx sys_reg_x
+	ldx SXREG
-	lda sys_reg_a
+	lda SAREG
 	plp
 
 	;; Call the routine.
-	jsr sys_jmp
+	jsr USRPOK
 	
 	jmp basic_execute_statement

c64/kernal/,aliases.s

@@ -3,30 +3,18 @@
 ;	(And only those for now that we feel the need to implement initially)
 ;	(https://www.c64-wiki.com/wiki/Zeropage)
 
-	.alias TXTTAB $2B
-	.alias IOSTATUS $90
-	; Keys down clears bits. STOP=bit 7, C= bit 6, SPACE bit 4, CTRL bit 2
-	.alias BUCKYSTATUS $91
 	.alias kernal_load_or_verify_flag $93
-	.alias C3PO  $94 ; flag - is BSOUR content valid
-	.alias BSOUR $95 ; serial bus buffered output byte
 	.alias current_file_num $98
-	.alias LDTND $98 ; number of entries in LAT / FAT / SAT tables
-	.alias DFLTN $99
 	.alias input_device_number DFLTN
-	.alias MSGFLG $9D ; bit 6 = error messages, bit 7 = control message
-	.alias jiffy_clock_24bits $a0
 	.alias cassette_buffer_bytes_used $A6
 	.alias load_or_scroll_temp_pointer $AC
 	;; We also use the following for temp colour pointer when scrolling
 	.alias load_save_verify_end_address $AE
 	.alias cassette_buffer_ptr $B2
-	.alias current_filename_length $B7
 	.alias current_logical_filenum $B8
 	.alias current_secondary_address $B9
 	.alias current_device_number $BA
 	.alias current_filename_ptr $BB
-	.alias load_save_start_ptr $C1
 	.alias load_save_end_ptr $C3
 	.alias last_key_matrix_position $C5
 	.alias keys_in_key_buffer $C6
@@ -54,24 +42,10 @@
 	.alias rs232_rx_buffer_ptr $F7
 	.alias rs232_tx_buffer_ptr $F9
 	
-	;; 2-byte location below seems to be a good place for temporary storage,
-	;; it seems used for timing during tape reads only - see:
-	;; - 'C64 Programmer's Reference Guide', page 314
-	;; - 'Compute's Mapping the Commodore 64', page 32
-	.alias CMP0 $B0 ;; $B0-$B1
-
-	;; Kernal tables for opened files, 10 entries each
-	.alias LAT $0259 ; logical file numbers
-	.alias FAT $0263 ; device numbers
-	.alias SAT $026D ; secondary addresses
-	
 	; "Compute's Mapping the 64" book
 	.alias keyboard_buffer $0277
-	.alias MEMSTR $0281
-	.alias MEMSIZ $0283 	; NOTE: Mapping the 64 erroniously has the hex as $282, while the DEC is correct
 	.alias text_colour $0286 ; p55
 	.alias colour_under_cursor $0287 ; p56
-	.alias HIBASE $0288     ; p56 (high byte of start of screen)
 	.alias key_buffer_size $0289 ; p57
 
 	;; 0 = cursor keys, insert, delete and space repeat, but nothing else
@@ -87,8 +61,6 @@
 	.alias keyboard_decoding_ptr $028F
 	.alias enable_case_switch $0291
 	.alias screen_scroll_disable $0292
-	.alias RSSTAT $0297 ; RS-232 status
-	.alias pal_or_ntsc $02A6
 
 	;; Under-ROM routines
 	;; (BASIC also includes them. XXX - We should de-duplicate them in a safe manner)

c64/kernal/load.s

@@ -19,7 +19,7 @@
 
 	;; Searching through Compute's Mapping the 64, we find the following
 	;; things are used:
-	;; $93 = kernal_load_or_verify_flag
+	;; $93 = VERCK
 	;; $AC = current pointer for loading/verifying
 	;; $C1 = similar to the above.
 
@@ -30,11 +30,11 @@
 load:
 
 	;; Are we loading or verifying?
-	sta kernal_load_or_verify_flag
+	sta VERCK
 
 	;; Store start address of LOAD
-	stx load_save_start_ptr+0
+	stx STAL+0
-	sty load_save_start_ptr+1
+	sty STAL+1
 
 	;; Reset status
 	jsr kernalstatus_reset
@@ -43,21 +43,8 @@ load:
 	jsr install_ram_routines
 
 	;; Display SEARCHING FOR + filename
-	lda MSGFLG
+	jsr lvs_display_searching_for
-	bpl +
-	jsr printf
-	.byte $0D,"SEARCHING FOR ",0
-	ldy #$00
-print_filename_loop:
 
-	cpy current_filename_length
-	beq +
-	ldx #<current_filename_ptr
-	jsr peek_under_roms
-	jsr JCHROUT
-	iny
-	jmp print_filename_loop
-*
 	;; http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
 	;; p13, 16; also p16 tells us this routine doesn't mess with the file table
 	;; in the C64, only in the drive.
@@ -65,20 +52,20 @@ print_filename_loop:
 	;; Call device to LISTEN (p16)
 	lda current_device_number
 	jsr listen
-	bcs load_device_not_found_error
+	bcs lvs_device_not_found_error
 
 	;; Open channel #0 (p16)
 	lda #$00
 	jsr tksa
-	bcs load_error
+	bcs lvs_load_verify_error
 
 	;; Send filename (p16)
 	ldy #0
 
-send_filename:
+load_send_filename:
 
-	cpy current_filename_length
+	cpy FNLEN
-	beq sent_filename
+	beq load_filename_sent
 
 	ldx #<current_filename_ptr
 	jsr peek_under_roms
@@ -90,7 +77,7 @@ send_filename:
 	pha
 
 	;; Set Carry flag on the last file name character, to mark EOI
-	cmp current_filename_length
+	cmp FNLEN
 	clc
 	bne +
 	sec
@@ -100,108 +87,66 @@ send_filename:
 
 	pla
 	tay
-	jmp send_filename
+	jmp load_send_filename
 
-sent_filename:
+load_filename_sent:
 
 	;; Command device to unlisten to indicate end of file name. (p16)
 	jsr unlsn
-	bcs load_error
+	bcs lvs_load_verify_error
 	jsr iec_set_idle ;; XXX is it needed?
 
 	;; Now command device to talk (p16)
 	lda current_device_number
 	jsr talk
-	bcs load_error
+	bcs lvs_load_verify_error
 
 	lda #$60 ; open channel / data (p3) , required according to p13
 	jsr iec_tx_command
-	bcs load_error
+	bcs lvs_load_verify_error
 
 	;; We are currently talker, so do the IEC turn around so that we
 	;; are the listener (p16)
 	jsr iec_turnaround_to_listen
-	bcs load_error
+	bcs lvs_load_verify_error
 
 	;; Get load address and store it if secondary address is zero
 	jsr iec_rx_byte
-	bcs load_file_not_found_error
+	bcs lvs_file_not_found_error
 	ldx current_secondary_address
 	beq +
-	sta load_save_start_ptr+0
+	sta STAL+0
 *
 	jsr iec_rx_byte
-	bcs load_file_not_found_error
+	bcs lvs_file_not_found_error
 	ldx current_secondary_address
 	beq +
-	sta load_save_start_ptr+1
+	sta STAL+1
 *
-	;; Display LOADING / VERIFYING and start address
+	;; Display start address
-	lda MSGFLG
+	jsr lvs_display_loading_verifying
-	bpl load_loop
-	lda kernal_load_or_verify_flag
-	beq +
-	jsr printf
-	.byte $0D, "VERIFYING", 0
-	jmp load_print_start_addr
-*
-	jsr printf
-	.byte $0D, "LOADING", 0
-load_print_start_addr:
-	jsr printf
-	.byte " FROM $",0
-	lda load_save_start_ptr+1
-	jsr printf_printhexbyte
-	lda load_save_start_ptr+0
-	jsr printf_printhexbyte
 
 load_loop:
 	;; We are now ready to receive bytes
 	jsr iec_rx_byte
-	bcs load_error
+	bcs lvs_load_verify_error
 
-	;; Save it and advance pointer.
+	;; Handle the byte (store in memory / verify)
-	;; As with our BASIC, we want to enable LOADing
+	jsr lvs_handle_byte_load_verify
-	;; anywhere in memory, including over the IO space.
+	bcs lvs_load_verify_error
-	;; Thus we have to use a helper routine in low memory
-	;; to do the memory access
 	
-	;; Save byte under ROMs and IO if required
+	;; Advance pointer to data
-	php
+	jsr lvs_advance_pointer
-	sei
+	bcs lvs_wrap_around_error
-	ldx #$33
-	stx $01
-	ldy #0
-	sta (load_save_start_ptr),y
-	ldx #$37
-	stx $01
-	plp
 
-	;; Advance pointer
-	inc load_save_start_ptr
-	bne +
-	inc load_save_start_ptr+1
-	;; If we wrap around to $0000, then this is bad.
-	beq load_wrap_around_error
-*
 	;; Check for EOI - if so, this was the last byte
 	lda IOSTATUS
 	and #K_STS_EOI
 	beq load_loop
 
-load_done:
 	;; Display end address
-	lda MSGFLG
+	jsr lvs_display_done
-	bpl +
+
-	jsr printf
-	.byte " TO $",0
-	lda load_save_start_ptr+1
-	jsr printf_printhexbyte
-	lda load_save_start_ptr+0
-	jsr printf_printhexbyte
-	lda #$0D
-	jsr JCHROUT
-*
 	;; Close file on drive
 
 	;; Command drive to stop talking and to close the file
@@ -214,7 +159,7 @@ load_done:
 	lda current_device_number
 	jsr listen
 
-	lda #$e0
+	lda #$E0
 	jsr iec_tx_command
 
 	;; Tell drive to unlisten
@@ -223,41 +168,5 @@ load_done:
 	;; Set IEC status back to idle
 	jsr iec_set_idle
 
-	;; Return last address - Compute's Mapping the 64 says without the '+1',
+	;; Return last address
-	;; checked (short test program) on original ROMs that this is really the case
+	jmp lvs_return_last_address
-	ldx load_save_start_ptr+0
-	ldy load_save_start_ptr+1
-
-	clc
-	rts
-
-load_wrap_around_error:
-
-	;; This error is probably not even detected by C64 Kernal;
-	;; report BASIC error code that looks the most sane
-	lda #B_ERR_OVERFLOW
-	sec
-	rts
-
-load_device_not_found_error:
-
-	jsr kernalstatus_DEVICE_NOT_FOUND
-	jmp kernalerror_DEVICE_NOT_FOUND
-
-load_file_not_found_error:
-
-	jmp kernalerror_FILE_NOT_FOUND
-
-load_error:
-
-	;; XXX should we really return BASIC error code here?
-	lda kernal_load_or_verify_flag
-	beq load_verify_error
-	lda #B_ERR_LOAD
-	bne +
-load_verify_error:
-	lda #B_ERR_VERIFY
-*	
-	sec
-	rts
-

c64/kernal/lvs_helpers.s

@@ -0,0 +1,128 @@
+
+;;
+;; Helper functions for various LOAD/VERIVY/SAVE routine variants (IEC / U64 / etc.)
+;;
+
+lvs_handle_byte_load_verify:
+
+	;; Save it and advance pointer.
+	;; As with our BASIC, we want to enable LOADing
+	;; anywhere in memory, including over the IO space.
+	;; Thus we have to use a helper routine in low memory
+	;; to do the memory access
+
+	;; Save byte under ROMs and IO if required
+	php
+	sei
+	;; XXX behavior should depend on address
+	ldx #$33
+	stx $01
+	ldy #0
+	sta (STAL),y
+	ldx #$37
+	stx $01
+	plp
+	rts
+
+lvs_advance_pointer:
+	;; Advance pointer
+	inc STAL
+	bne lvs_success_end
+	inc STAL+1
+	;; If we wrap around to $0000, then this is bad.
+	beq lvs_error_end
+*
+	clc
+	rts
+
+lvs_display_searching_for:
+	lda MSGFLG
+	bpl lvs_display_end
+	jsr printf
+	.byte $0D,"SEARCHING FOR ",0
+	ldy #$00
+*
+	cpy FNLEN
+	beq lvs_display_end
+	ldx #<current_filename_ptr
+	jsr peek_under_roms
+	jsr JCHROUT
+	iny
+	jmp -
+
+lvs_display_end:
+	rts
+
+lvs_display_loading_verifying:
+	;; Display LOADING / VERIFYING and start address
+	lda MSGFLG
+	bpl lvs_display_end
+	lda VERCK
+	beq +
+	jsr printf
+	.byte $0D,"VERIFYING",0
+	jmp lvs_display_start_addr
+*
+	jsr printf
+	.byte $0D,"LOADING",0
+	;; FALLTHROUGH
+	
+lvs_display_start_addr:
+	jsr printf
+	.byte " FROM $",0
+	lda STAL+1
+	jsr printf_printhexbyte
+	lda STAL+0
+	jmp printf_printhexbyte
+
+lvs_display_done:
+	;; Display end address
+	lda MSGFLG
+	bpl lvs_display_end
+	jsr printf
+	.byte " TO $",0
+	lda STAL+1
+	jsr printf_printhexbyte
+	lda STAL+0
+	jsr printf_printhexbyte
+	lda #$0D
+	jmp JCHROUT
+
+lvs_wrap_around_error:
+	;; This error is probably not even detected by C64 Kernal;
+	;; report BASIC error code that looks the most sane
+	lda #B_ERR_OVERFLOW
+lvs_error_end:
+	sec
+	rts
+
+lvs_return_last_address:
+	;; Return last address - Compute's Mapping the 64 says without the '+1',
+	;; checked (short test program) on original ROMs that this is really the case
+	ldx STAL+0
+	ldy STAL+1
+	;; FALLTHROUGH
+
+lvs_success_end:
+	clc
+	rts
+
+lvs_device_not_found_error:
+
+	jsr kernalstatus_DEVICE_NOT_FOUND
+	jmp kernalerror_DEVICE_NOT_FOUND
+
+.alias lvs_file_not_found_error kernalerror_FILE_NOT_FOUND
+
+lvs_load_verify_error:
+	;; XXX should we really return BASIC error code here?
+	lda VERCK
+	beq lvs_verify_error
+	lda #B_ERR_LOAD
+	bne lvs_error_end
+	;; FALLTHROUGH
+
+lvs_verify_error:
+	lda #B_ERR_VERIFY
+	sec
+	rts

c64/kernal/scan_keyboard.s

@@ -334,7 +334,7 @@ next_row:
 	;; so that RUN/STOP etc can be checked easily
 	;; (Compute's Mapping the 64, p27)
 	lda ScanResult+0
-	sta BUCKYSTATUS
+	sta STKEY
 
 	;; Store de-bounce data for bucky keys
 	;; (Compute's Mapping the 64, p58-59)

c64/kernal/setnam.s

@@ -13,8 +13,8 @@ setnam:
 	;; There are 6 sane ways to implement this routine,
 	;; I hope this one won't cause similarity to CBM code
 
-	sta current_filename_length
+	sta FNLEN
-	sty current_filename_ptr + 1
+	sty STAL + 1
-	stx current_filename_ptr + 0
+	stx STAL + 0
 
 	rts

c64/kernal/stop.s

@@ -9,11 +9,11 @@
 ;;
 
 stop:
-	;; Bit 7 of BUCKYSTATUS contains the state of the STOP key
+	;; Bit 7 of STKEY contains the state of the STOP key
 	;; (Compute's Mapping the 64, p27)
 
 	;; BASIC checks carry flag to indicate STOP or not
-	lda BUCKYSTATUS
+	lda STKEY
 	and #$80
 	beq stop_pressed