Hello all

[thomasparlette]

Hello all I am new to the 6502 world. I just started building my own SY6502 system. So far I have the SY6502 running at 2MHz with an SY6522 wired up on a bread board. I also wired up an 28HC64 EEPROM. Still working on the RAM (waiting on another breadboard to show up. I have also started to wire up the 6551 and some 7-segment displays.

I already tested the 6522 with producing a frequency at PB7 and some basic on off stuff on port B.

One issue I am running into is with the BNE instruction. I am trying to make a simple delay program to display 1-9 on a single 7-segment display attached to port B but it seems like it's getting stuck at the first point.

[barrym95838]

Maybe that LDA $50 at Next: should be LDX $50 ??

Mike B.

[thomasparlette]

Lol wow yea I just saw that. Thanks I will try that and let you know.

[thomasparlette]

I looked at my code again and I am just loading A with data from location 50 then checking to see if the data at that point is 10 or more. Then displaying the number. I tried changing to to LDX and it still didn't work. I scaled down the program a lot just to check the function of the Delay task. Listed below is the new code I am using to test out the Delay program.

From what I can figure out its is getting to LDA #$66 and just stopping at that point. I am using SB-Assembler to assemble the code. I also Tried a few other assemblers but they all produce the same thing. I even tried just put in the code byte by byte into my programmer and still same results.

Code: Select all

MSCNT .EQ	199
	.OR $E000
	LDA	#0
	STA	PCR
	LDA	#$FF
	STA	DDRB
	LDA	#$66
	JSR Delay
	STA	PORTB
	LDA	#$6D
	STA	PORTB	
	BRK
Delay:
	LDX	#MSCNT
DLY1:
	DEX
	BNE	DLY1
	DEY
	BNE	Delay
	RTS

[thomasparlette]

Update I programmed the ROM with a lot of NOP codes in place of the jumps commands to just retest to make sure it is not an hardware issue and I got it to change the display. So I think it may be something todo with my jump code that is causing the issue but just can't figure out what it is.

Thanks again for the help

[BigEd]

Welcome, Thomas! I notice you use a DEY as an outer loop, but you don't initialise Y beforehand - that means we don't quite know how often it will go around.

[thomasparlette]

ok I see that issue Here is the updated code. I am still having the same issue.

Code: Select all

	.CR	6502
	.TF	c:\sbasm3\Projects\Bin\test.bin,BIN
	.IN c:\sbasm3\Projects\Include\VIA_Setup.65s
MSCNT .EQ	199
YCNT  .EQ	1
	.OR $0000
	LDA	#0
	STA	PCR
	LDA	#$FF
	STA	DDRB
Start:	LDA	#$66
	STA	PORTB
	LDY YCNT
	JSR Delay
	LDA	#$6D
	STA	PORTB
	LDY	YCNT
	JSR Delay
	JMP	Start
Delay:
	LDX	#MSCNT
DLY1:
	DEX
	BNE	DLY1
	DEY
	BNE	Delay
	RTS		

[BigEd]

You might want to double-check that the addresses are right. You have
.OR $E000
in one version and
.OR $0000
in another. Do you know what address the ROM is actually mapped to in the hardware? The JSR takes an absolute address, so that has to match the actual memory map of the machine when it's running. On the other hand, when you're programming the EEPROM your image starts at the beginning of the ROM. You need to be sure you've prepared an image which starts at the appropriate address: the 24th byte of the ROM might be address $E018 for example.

[barrym95838]

Maybe those LDY YCNTs should be LDY #YCNT ??

Mike B.

[thomasparlette]

Yea they are I made a small mistake retypeing in on my other computer I don't have internet (network card failed) on my programming machine so I retypeing in the code when I made that post here sorry about that.

[leepivonka]

Remember that JSR & RTS use the 6502 stack. If you don't have RAM at $0100..$01FF, the stack won't work & RTS will jump to some strange address.
Instead of using JSR to call the delay routine, you could inline a copy of the routine at both places where it is used.

[thomasparlette]

I was rereading GARTHWILSON Primer again this morning and realized the same thing. Tonight I am hopping to wire up the RAM but until then I made the following changes to test before adding more I/C's.

Code: Select all

; Assembler Setup & Configure
	.CR	6502
	.TF	C:\Software\sbasm3\Projects\Bin\test_2.bin,BIN
	.IN C:\Software\sbasm3\Projects\Include\VIA_Setup.65s
; Variables 
MSCNT 	.EQ   	199
YCNT  	.EQ   	1
; Start of Program
		.OR 	$E000
		LDA   	#0
		STA   	PCR
		LDA   	#$FF
		STA   	DDRB
Start 	LDA   	#$66
		STA   	PORTB
		LDY 	YCNT
		JMP 	Delay1
Return1	LDA   	#$6D
		STA   	PORTB
		LDY   	YCNT
		JMP   	Delay2
; Delay's
Delay1 	LDX   	#MSCNT
DLY1   	DEX
		BNE   	DLY1
		DEY
		BNE   	Delay1
		JMP 	Return1
Delay2 	LDX   	#MSCNT
DLY2   	DEX
		BNE   	DLY2
		DEY
		BNE   	Delay2
		JMP 	Start 
; 6502 Hardware Vectors
		.NO 	$FFFA
		.DB 	$00, $00 ; NMI Vector
		.DB 	$00, $E0 ; Reset Vector
		.DB 	$00, $00 ; IRQ Vector