Need help with ASM code

richaj45 · 2008-01-15 06:37

I need help to get the best asm code for the following:

1) Declare 12-bit label values stored in program memory.
2) Index into the table of values with a 8-bit number.
3) Read the 12-bit value with iread.
4) Jump to the 12-bit value as a program memory location and start
execution.

I am new to the SX ASM so could i get help in making this as fast as possible.

cheers,
rich

[noparse][[/noparse]edit] Rich, I added a subject to your post. Bean.

Post Edited By Moderator (Bean (Hitt Consulting)) : 1/15/2008 12:50:31 PM GMT

Bean · 2008-01-15 13:52

richaj45 said...
I am new to the SX ASM so could i get help in making this as fast as possible.

Rich,
· Do you want a quick reply ? Or do you want the CODE to execute quickly ?

· Here is some output from SX/B to do it. I'm sure it not the as fast as it could be.

 
    55  =0000000D       temp1         EQU  0x0D          ;temp1   VAR BYTE
    56                  
    57  =0000000E       tempW         EQU  0x0E          ;tempW   VAR WORD
    58  =0000000E       tempW_LSB     EQU  tempW        
    59  =0000000F       tempW_MSB     EQU  tempW+1      
    60                  
    61                  
    62  07FF  0A00      RESET __PROGSTART                ;PROGRAM Start NOSTARTUP
    63  =00000000       __PROGSTART:                    
    64  0000  0CF7        MOV FSR,#__TRISA              
        0001  0024
    65  0002  0CFF        MOV IND,#255                  
        0003  0020
    66  0004  02A4        INC FSR                       
    67  0005  0020        MOV IND,W                     
    68  0006  02A4        INC FSR                       
    69  0007  0020        MOV IND,W                     
    70  0008  0064        CLR FSR                       
    71  0009  0010        JMP @Start                    
        000A  0A0D
    72  =0000000D         ORG $+2  ; FOR DEBUGGER       
    73                  
    74                  
    75  =0000000D       Start:                           ;Start:
    76                  
    77  000D  0C02        MOV temp1,#2                   ;  temp1 = 2
        000E  002D
    78                  
    79                  
    80  000F  0403        CLC                            ;  temp1 = temp1 << 1
    81  0010  036D        RL temp1                      
    82                  
    83  0011  0C33        MOV __PARAM1,#Table & 255      ;  READ Table + temp1, tempW
        0012  0028
    84  0013  0C00        MOV __PARAM2,#Table >> 8      
        0014  0029
    85  0015  020D        ADD __PARAM1,temp1            
        0016  01E8
    86  0017  0603        ADDB __PARAM2,C               
        0018  02A9
    87  0019  0209        MOV M,__PARAM2                
        001A  0043
    88  001B  0208        MOV W,__PARAM1                
    89  001C  0041        IREAD                         
    90  001D  002E        MOV tempW_LSB,W               
    91  001E  02A8        INC __PARAM1                  
    92  001F  0643        ADDB __PARAM2,Z               
        0020  02A9
    93  0021  0209        MOV M,__PARAM2                
        0022  0043
    94  0023  0208        MOV W,__PARAM1                
    95  0024  0041        IREAD                         
    96  0025  002F        MOV tempW_MSB,W               
    97                  
    98  0026  0403        CLC                            ;  temp1 = temp1 >> 1
    99  0027  032D        RR temp1                      
   100                  
   101                  
   102  0028  020F        MOV M,tempW_MSB                ;  READ tempW, temp1
        0029  0043
   103  002A  020E        MOV W,tempW_LSB               
   104  002B  0041        IREAD                         
   105  002C  002D        MOV temp1,W                   
   106                  
   107                  
   108  002D  0010        JMP @$                         ;END
        002E  0A2D
   109                  
   110                  
   111  =0000002F       DATA0:                           ;DATA0:
   112                  
   113  002F  0080        DW 128                         ;  DATA 128
   114                  
   115  =00000030       DATA1:                           ;DATA1:
   116                  
   117  0030  0081        DW 129                         ;  DATA 129
   118                  
   119  =00000031       DATA2:                           ;DATA2:
   120                  
   121  0031  0082        DW 130                         ;  DATA 130
   122                  
   123  =00000032       DATA3:                           ;DATA3:
   124                  
   125  0032  0083        DW 131                         ;  DATA 131
   126                  
   127                  
   128  =00000033       Table:                           ;Table:
   129                  
   130  0033  002F        DW (DATA0 & 255),(DATA0 >> 8),(DATA1 & 255),(DATA1 >> 8),(DATA2 & 255),(DATA2 >> 8),(DATA3 & 255),(DATA3 >> 8) ;  DATA DATA0, DATA1, DATA2, DATA3
        0034  0000 0030 0000 0031
        0038  0000 0032 0000
   131

Bean.
·

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Post Edited (Bean (Hitt Consulting)) : 1/15/2008 1:58:11 PM GMT

richaj45 · 2008-01-15 16:26

I don't need a quick reply but i do need the asm to run as fast as possible.

cheers,
rich

BillXGS · 2008-01-18 06:20

I hang around the XGameStation board and lurk over here once in awhile,
but found this programming challenge too tasty to resist registering
just to answer.

A general way of doing a jump table with an SX in not easy.

But if you can live with a few constraints, it can be done fairly
efficiently.

1. You are limited to no more than 126 entries in your table
2. You must allocate a scratch file register; I will call it Scratch

;
; Call with index in W
;
Dispatch:
mov Scratch,W ; Double the index
add W,Scratch
add PC,W ; Jump to vector

page Entry0
jmp Entry0

page Entry1
jmp Entry1

page Entry2
jmp Entry2

:
:
:

Bill

Guenther Daubach · 2008-01-18 08:40

Bill,

the code can be modified to avoid the Scratch register:

mov !option, #%01011111 ; clear option.7 to map w into 01h

Dispatch
clc
rl wreg ; Note: you must use "wreg", SASM will generate wrong code when you use "w" here
add pc, w

page Entry0
jmp Entry0
;
;
;

As long as most jump targets are located in the same page where the dispatcher is located, you can even simplify the code but still handle cases where some code is outside the current page:

Dispatch
add pc, w

jmp Entry0

jmp Entry1

jmp Entry2

Entry0
;
;

Entry1
;
;

Entry2 ; This is an intermediate target - the remaining code for Entry2 is located in another page
page _Entry2
jmp _Entry2
;
;

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Greetings from Germany,

G

BillXGS · 2008-01-18 11:54

Gnther,

True, but he did not specific which particular processor he was using. That option is not available with the SX-48 or SX-52. Or he may need access to the RTCC register.

BillXGS · 2008-01-18 12:10

If the index was already in a file register instead of W, then just do this:

mov W,Index
add W,Index
add PC,W
:
:
:

Bean · 2008-01-18 12:27

BillXGS said...
Gnther,

True, but he did not specific which particular processor he was using. That option is not available with the SX-48 or SX-52. Or he may need access to the RTCC register.

Welcome Bill,
· The SX48 and SX52 also allow using WREG by setting the bit in the OPTION registers. Just for the book.

Bean.

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·

richaj45 · 2008-01-18 17:20

Thank you much for the great response.

At first thought, i would have looked at using the iread instruction so a jump table would not be needed.

When is the iread instruction used.

cheers,
rich

James Newton · 2008-01-18 19:44

http://www.sxlist.com/techref/ubicom/lib/mem/tables_sx.htm explains it all.

bitnum2mask
;load lower byte of address plus index
mov temp, W ;store index 
mov W, #table_start && $FF ;w = lower byte of table start address
add W, temp ;add index to w

mov M, #table_start >> 8 ;load higher address of table
snb C
mov M, #table_start >> 8 + 1 ;correct if carry

IREAD ;read table to M:W

mov M, #$0F ;restore MODE to default
table_start
dw 1, 2, 4, 8, 16, 32, 64, 128

Better ways are available with macros:
http://www.sxlist.com/techref/ubicom/keymacs.src·

The LookupW macro conditionally·leaves out the snb and second mov when they are not needed.

The GotoW macro automatically compiles the most efficient possible jump table (not IREAD) given some supporting defines and sub macros. It's complicated to understand/explain, but it works very easily and always produces the best possible code.

There are also IF / THEN / ELSE·/ CASE and all that macros.. not that anyone would bother...

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---
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james at sxlist,com 1-619-652-0593 fax:1-208-279-8767
SX FAQ / Code / Tutorials / Documentation:
http://www.sxlist.com Pick faster!

Need help with ASM code

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