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| need help with 8051 macro assembler [message #10529] |
Tue, 05 December 2023 15:02  |
lynchaj
Messages: 1080
Registered: June 2016
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Senior Member |
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Hi
I am working on a SAB80535 dev board and would like to port Tiny BASIC to it. The PJRC 8051 dev board has Tiny BASIC here:
https://www.pjrc.com/tech/8051/contrib/tb51/index.html
the Intel Hex file does not properly on my SAB80535 because the memory map is different than the PJRC 8051 dev board.
The PJRC 8051 dev board has RAM at 0x0000 to 07FFF and ROM at 0x8000 to 0xF7FF.
However, my SAB80535 relies on external ROM only it has ROM at 0x0000 to 0x7FFFF and RAM at 0x8000 to 0xF7FF
When I run the Tiny BASIC executable on my SAB80535 dev board, it seems to work but when you "LIST" a simple program, Tiny BASIC doesn't seem to remember the program you just entered.
Looking at the tb51.asm, I think the reason is obvious; it is trying to store program data and variables in the RAM area, which is actually ROM on my board, and it is not getting recorded.
The solution should be to adjust the tb51.asm code but I am not very familiar with Macro Assembler and that's where I need some help.
I found a Macro Assembler for 8051 here:
http://plit.de/asem-51/home.htm
If I comment out the first line "$MOD52", then it assembles clean with no errors but the resulting executable behaves the same as before. If I change the lines
EXTRAM EQU 2034H ;External program buffer begins after 26 vars.
RAMLIM EQU 3000H ;Allowance made for 4K RAM buffer.
to
EXTRAM EQU 0A034H ;External program buffer begins after 26 vars.
RAMLIM EQU 0B000H ;Allowance made for 4K RAM buffer.
Then the Tiny BASIC will at least remember a program I type in. However, I think there is another problem at this line:
DSEG
ORG 20H
I think it is trying to store data over the ROM location at 0x0020. Somehow, I need to find a way to move this data segment into RAM at 0xC000. There is a similar problem here at this line:
ORG 30H
Does someone know Macro Assembler well enough to help me move the data segments to the RAM region at 0xC000? Better yet, store it at the end of the Tiny BASIC code at 0x8000 in a special data segment?
Thanks in advance for any help. Much appreciated. Andrew Lynch
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| Re: need help with 8051 macro assembler [message #10542 is a reply to message #10534] |
Fri, 08 December 2023 14:29  |
trianon
Messages: 20
Registered: May 2020
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Junior Member |
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Hi,
Been many years I used to program the SAB80517A (upgrade version of the 535) in assembler, some things that come to mind :
The 8051 processor a Harvard architecture, meaning it has 64K code space & 64K data space ! (And 256 bytes internal RAM, first 128bytes are R0~R7 over 4 banks + some bits & last 128b as stack or indirect addressing.
The code starts at $8000 in the assembler :
CSEG
ORG 8000H
JMP S_INIT ;Jump to system initialization routine.
You can change this to $0000 if you want to store it in flash/eeprom at $0000, I know some cheap development boards don't decode A15 so code compiled for $8000 will also run like it's in $0000.
I have not fully check all source code, but I found already :
This code below puts the high byte of the address fixed on P2 port = 8 bit high address port
STREXT: MOV R1,A
DD001: MOV P2,#HIGH(EXTRAM)
MOV A,TMP0
MOVX @R1,A
INC R1 ;Bump pointers.
MOV A,TMP1 ;Move high-order byte into variable array.
MOVX @R1,A
RET
Same happens during memory init :
RAM_INIT:
CLR A ;Many bytes to be cleared...
MOV MODE,A ;Interactive mode, decimal radix.
MOV FLAGS,A ;Interroutine flags.
DD010: MOV P2,#HIGH(EXTRAM);Select first External RAM page.
MOV R0,A
MOV A,#5AH ;Random bit pattern.
MOVX @R0,A
MOVX A,@R0
XRL A,#5AH
JZ EXTINI
CLR A
MOV R0,#US_VAR ;Clear variable array.
INIT_1: MOV @R0,A
INC R0
CJNE R0,#US_VAR+2*NO_VAR,INIT_1 ;Loop until all vars cleared.
SJMP INIT_3
This means you need to change
EXTRAM EQU 2034H
to
EXTRAM EQU 8034H
This is the code to start at the first line of code, changing EXTRAM should also work here.
;REWIND
; Reset Cursor to start of current program buffer space.
;
REWIND: CLR CHAR_FLG
JB ROMMOD,REWROM
MOV PNTR_H,#HIGH(EXTRAM)
MOV PNTR_L,#LOW(EXTRAM)
RET
What to look for in source code is :
MOVC is to read data from CODE memory
MOVX is to read or write data from/to RAM
And if this is not strange enough (compared to 68000) on may development boards they added logic to have the RAM access possible in both code and RAM.
For example EEPROM at $0000 so it will boot and RAM at $8000 at both code and data, this way the bootloader could download hex files over serial port,
store it in the RAM by MOVX. Once all hex files are stored, you can run it out of ram because.
If this additional logic (PSEN and RD) would not be implemented you could not run code out of RAM.
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| Re: need help with 8051 macro assembler [message #10544 is a reply to message #10543] |
Sun, 10 December 2023 10:13 |
lynchaj
Messages: 1080
Registered: June 2016
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Senior Member |
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Hi
Experimenting some more with Tiny BASIC on the SAB80535 dev board. I tried changing EXTRAM to 8034H but no luck. With that change, tiny BASIC does not start when I jump to it from PAULMON2.
I have had some luck with the changes I've made below
Lines 1-9, I commented out line 1 and added 7 and 8
; $MOD52
$NODEBUG
$PAGEWIDTH (120)
$PAGELENGTH (66)
$TITLE (Tiny-Basic51 - Modified for Metalink ASM51)
$NOMOD51
$INCLUDE (80515.MCU)
Then I made these changes to lines 194, 195, and 196
EXTRAM EQU 2034H+7000H ;External program buffer begins after 26 vars.
RAMLIM EQU 3000H+7000H ;Allowance made for 4K RAM buffer.
EXTROM EQU 9080H+3000H ;Start of external ROM space.
I added 7000H to EXTRAM and RAMLIM pushing those deeper into RAM space. Tiny BASIC itself occupies between 8000H and 8FFFH approximately according to the LST file.
When I start the SAB80535 dev board and upload the Tiny BASIC hex file to the RAM (8000-F7FF) I get this:
Welcome to PAULMON2 v2.1, by Paul Stoffregen
See PAULMON2.DOC, PAULMON2.EQU and PAULMON2.HDR for more information.
Program Name Location Type
List 1000 External command
Single-Step 1400 External command
Memory Editor (VT100) 1800 External command
PAULMON2 Loc:2000 >
PAULMON2 Loc:2000 >
PAULMON2 Loc:2000 > New location
New memory location: 8000
PAULMON2 Loc:8000 > Download
Begin ascii transfer of Intel hex file, or ESC to abort
Download completed
Summary:
202 lines received
3202 bytes received
3202 bytes written
No errors detected
PAULMON2 Loc:8000 >
PAULMON2 Loc:8000 > Jump to memory location
Jump to memory location (8000), or ESC to quit: 8000
running program:
MCS-51 TINY BASIC/Metalink-Compatible Source V2.3
OK
>
So far, so good. It looks like it is working. So I type in a simple program, list it, and run it
OK
>10 I=5
>20 PRINT "HELLO WORLD", I
>LIST
10 I=5
20 PRINT "HELLO WORLD", I
OK
>RUN
HELLO WORLD 5
WHAT?
OK
>
but notice I get the WHAT? indicating some kind of error. I can add more to the program like this
OK
>10 I=5
>20 PRINT "HELLO WORLD", I
>LIST
10 I=5
20 PRINT "HELLO WORLD", I
OK
>RUN
HELLO WORLD 5
WHAT?
OK
>
It looks like it is mostly working but for some reason some variable is getting corrupted or not stored properly in the first place. It is so close to working but just not quite.
Notice, even if I delete the variable and just leave the regular program statements, I still get the WHAT? error
OK
>LIST
10 I=5
20 PRINT "HELLO WORLD", I
30 I=I+1
40 GOTO 20
OK
>10
>30
>LIST
20 PRINT "HELLO WORLD", I
40 GOTO 20
OK
>RUN
HELLO WORLD 5
WHAT?
OK
>
Any ideas and/or suggestions? Thanks, Andrew Lynch
PS, I've had a major breakthrough event, I noticed line 321 is "SETB ROMMOD" so I commented it out and replaced it with "CLR ROMMOD" and now the Tiny BASIC sample program runs just fine. The funny thing is the code in the RUNROM subroutine and there doesn't appear to be any obvious way for that routine to get executed. It looks like dead code but apparently not. RUNROM is only called from one line, and it is commented out. The line above it is a JMP instruction so how the MCU is getting to that routine in quite mysterious. But it works so I'll take it!
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Attachment: tb51a.asm
(Size: 63.82KB, Downloaded 120 times)
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Attachment: tb51.asm
(Size: 63.77KB, Downloaded 128 times)
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Attachment: tb51a.lst
(Size: 145.67KB, Downloaded 121 times)
[Updated on: Sun, 10 December 2023 16:31] Report message to a moderator |
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