implemented MERGE command

c64/basic/basic_commands/cmd_load_verify.s

@@ -50,6 +50,9 @@ cmd_load_got_params:                   // input for tape wedge
 
 	ldy TXTTAB+1
 	ldx TXTTAB+0
+
+cmd_load_loadmerge:                    // entry point for 'cmd_merge'
+
 	lda VERCKB    // LOAD or VERIFY
 
 	jsr JLOAD

c64/basic/basic_commands_CC/cmd_bload.s

@@ -1,8 +0,0 @@
-// #LAYOUT# STD *       #TAKE
-// #LAYOUT# *   BASIC_0 #TAKE
-// #LAYOUT# *   *       #IGNORE
-
-
-cmd_bload:
-
-	jmp do_NOT_IMPLEMENTED_error // XXX implement the command

c64/basic/basic_commands_CC/cmd_bload_bverify.s

@@ -0,0 +1,41 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+
+cmd_bverify:
+
+	// LOAD and VERIFY are very similar, from BASIC perspective there is almost no difference;
+	// just different parameter passed to Kernal and different error message in case of failure
+
+	lda #$01                           // mark operation as VERIFY
+	skip_2_bytes_trash_nvz
+
+cmd_bload:
+
+	lda #$00                           // mark operation as LOAD
+	sta VERCKB
+
+	// Set default device and secondary address; channel is not important now
+
+	jsr select_device
+	ldy #$00                           // secondary address 0 - it has to be loaded precisely where we want
+	jsr JSETFLS
+
+	// Fetch the file name
+
+	jsr fetch_filename
+	bcc !+
+
+	// No filename supplied - this should only be allowed for tape (device number below 8)
+
+	lda FA
+	and #%11111000
+	bne_16 do_MISSING_FILENAME_error
+
+	lda #$00
+	sta FNLEN
+!:
+	// XXX finish the implementation
+
+	jmp do_NOT_IMPLEMENTED_error

c64/basic/basic_commands_CC/cmd_bverify.s

@@ -1,8 +0,0 @@
-// #LAYOUT# STD *       #TAKE
-// #LAYOUT# *   BASIC_0 #TAKE
-// #LAYOUT# *   *       #IGNORE
-
-
-cmd_bverify:
-
-	jmp do_NOT_IMPLEMENTED_error // XXX implement the command

c64/basic/basic_commands_CC/cmd_merge.s

@@ -5,4 +5,46 @@
 
 cmd_merge:
 
-	jmp do_NOT_IMPLEMENTED_error // XXX implement the command
+	lda #$00                           // mark operation as LOAD
+	sta VERCKB
+
+	// Set default device and secondary address; channel is not important now
+
+	jsr select_device
+	ldy #$00                           // secondary address 0 - it has to be loaded precisely where we want
+	jsr JSETFLS
+
+	// Fetch the file name
+
+	jsr fetch_filename
+	bcc !+
+
+	// No filename supplied - this should only be allowed for tape (device number below 8)
+
+	lda FA
+	and #%11111000
+	bne_16 do_MISSING_FILENAME_error
+
+	lda #$00
+	sta FNLEN
+!:
+	// Fetch device number
+
+	jsr fetch_device_secondary_uint8
+	bcs !+
+
+	sta FA
+!:
+	// Perform loading - just for a different address
+
+	sec
+	lda VARTAB+0
+	sbc #$02
+	sta VARTAB+0
+	tax
+	bcs !+
+	dec VARTAB+1
+!:
+	ldy VARTAB+1
+
+	jmp cmd_load_loadmerge                    // XXX check variable handling (VARTAB) after failure to load

c64/basic/engine/fetch_device_secondary.s

@@ -11,15 +11,9 @@ fetch_device_secondary:
 
 	// Fetch the device number
 
-	jsr injest_comma
-	bcs fetch_secondary
+	jsr fetch_device_secondary_uint8
+	bcs fetch_device_secondary_done
 
-	jsr injest_spaces
-	jsr basic_parse_line_number
-	lda LINNUM+1
-	bne_16 do_ILLEGAL_QUANTITY_error
-
-	lda LINNUM+0
 	sta FA
 
 	// FALLTROUGH
@@ -28,15 +22,9 @@ fetch_secondary:
 
 	// Fetch secondary address
 
-	jsr injest_comma
+	jsr fetch_device_secondary_uint8
 	bcs fetch_device_secondary_done
 
-	jsr injest_spaces
-	jsr basic_parse_line_number
-	lda LINNUM+1
-	bne_16 do_ILLEGAL_QUANTITY_error
-
-	lda LINNUM+0
 	sta SA
 
 	// FALLTROUGH
@@ -44,3 +32,18 @@ fetch_secondary:
 fetch_device_secondary_done:
 
 	rts
+
+
+fetch_device_secondary_uint8: // also called by 'cmd_merge'
+
+	jsr injest_comma
+	bcs !+
+
+	jsr injest_spaces
+	jsr basic_parse_line_number
+	lda LINNUM+1
+	bne_16 do_ILLEGAL_QUANTITY_error
+	lda LINNUM+0
+	clc
+!:	
+	rts