How could I make a adjustable delay function in "micro-second" level

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Read-Only Author Jason Yang Posted 17-Jan-2005 08:51 GMT Toolset C51	How could I make a adjustable delay function in "micro-second" level Jason Yang Hello Every : I use AT89C52 and 11.059MHz oscillator. 1 instuction takes about 1 micro-second.(10^-6 sec.) I write a delay function in *.asm. It works well , but I want it adjustable. I want to delay according to the parameter I pass.My goal is to modify delay time for some protocol time slot testing. I found it some how difficult to achieve. Because the basic instruction , for example : _nop_ , take 1 micro-second. I can't add more decision. It will takes more time. How could I implement such kind of delay? Please give me a hand , thanks a lot~~

Read-Only Author Andrew Neil Posted 17-Jan-2005 10:02 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Andrew Neil Sounds like you need to use a faster processor, and/or one that uses less clock cycles per instruction. Maybe you could use a timer, but you'll still have difficulties if the delays are on the same order as the execution time of a single instruction! Maybe some external hardware to do the critical timing? Take a look at this thread: http://www.keil.com/forum/docs/thread2938.asp

Read-Only Author Drew Davis Posted 17-Jan-2005 17:38 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Drew Davis You might try a series of _nops_, and jump far enough down into them so that the remainder represents the time that you need. There is still some overhead in this method, of course. You have to calculate the jump, and get into and out of the function. You won't be able to create a 1 us delay, but you might be able to create fairly precise delays from, say, 10 us up to as long of a table as you can stand. Longer intervals means you can use a loop, at the cost of more granularity and more overhead. Small intervals and precise measurements are best done by timer hardware rather than software. "Small" is relative to your processor clock and architecture. If software has to act at very precise times (send this response exactly 3.4 microseconds after receiving this message), then you need a faster processor, as Andrew suggests. There is an overall system design issue to be considered here, so it's hard to suggest solutions without really knowing the requirements.

Read-Only Author erik malund Posted 17-Jan-2005 17:52 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level erik malund I want to delay according to the parameter I pass.My goal is to modify delay time for some protocol time slot testing. For delays this short the only option is inline nop. two possibilities 1) Since you refer to "testing" could you use a conditional assembly. 2) Selecting the routine instead of selecting the delay: do_it_with_1 mov... ... .... ... nop ... ... ... ... ret do_it_with_2 mov... ... .... ... nop nop ... ... ... ... ret Erik

Read-Only Author erik malund Posted 17-Jan-2005 17:53 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level erik malund oh, even easier do_it_with_1 MACRO_1 nop MACRO_2 do_it_with_2 MACRO_1 nop nop MACRO2 Erik

Read-Only Author Tim-Oliver Paaschen Posted 19-Jan-2005 06:27 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Tim-Oliver Paaschen Take a look at the following thread: http://www.keil.com/forum/docs/thread1940.asp It has some interesting macros to convert microseconds to instruction cylcles and to place the appropriate number of NOPs into your code.

Read-Only Author Jon Ward Posted 20-Jan-2005 16:50 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Jon Ward Just for grins, I created the following assembler file using MPL macros: NAME NOPS ?PR?NOPS?NOPS SEGMENT CODE RSEG ?PR?NOPS?NOPS %DEFINE (GenNops) ( %SET (cnt, 200) %WHILE (%cnt GT 0) ( %SET(b_ones,(%cnt / 1) mod 10) %SET(b_tens,(%cnt / 10) mod 10) %SET(b_huns,(%cnt / 100) mod 10) PUBLIC NOPS_%substr(%b_huns,2,1)%substr(%b_tens,2,1)%substr(%b_ones,2,1) NOPS_%substr(%b_huns,2,1)%substr(%b_tens,2,1)%substr(%b_ones,2,1): nop %SET (cnt, %cnt - 1) ) ) %GenNops RET END When youassemble this file, you'll get something like the following: 19 PUBLIC NOPS_200 0000 00 20 NOPS_200: nop 21 22 PUBLIC NOPS_199 0001 00 23 NOPS_199: nop 24 25 PUBLIC NOPS_198 0002 00 26 NOPS_198: nop 27 28 PUBLIC NOPS_197 0003 00 29 NOPS_197: nop . . . 613 PUBLIC NOPS_002 00C6 00 614 NOPS_002: nop 615 616 PUBLIC NOPS_001 00C7 00 617 NOPS_001: nop 618 619 620 00C8 22 621 RET The assembler file is simply a table of NOP instructions with a public label for each. You can control how many are generated with the %SET (cnt, 200). The only overhead for calling a "function" in this table is the time it takes to execute the CALL and RET instructions. The following shows how to delay for 10 NOPs (plus the CALL and RET). extern void NOPS_010 (void); void main (void) { while (1) { NOPS_010 (); } } An improvement which could be made to this is to change the labels so that there was no 0 prefix for numbers less than 100. Jon

Read-Only Author Jason Yang Posted 21-Jan-2005 03:12 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Jason Yang Thank You all , I learned a lot from you all. But Jon , Maybe you just solved half of my question. All of You did give me some great solution of how to delay in micro-second level. But , I still can't decide "delay count" in run time. Your method is calling certain non-parametered sub-routine in the program. For example , if I want to delay 10 uS , I could call NOPS_010 (),and 20 uS ,call NOPS_020(). This is great when implementing any protocol. But , if I want to adjust Signal time slot (protocol) in run time. I want to input "delay count" to decide how long to delay. I tried the method in this article : http://www.keil.com/forum/docs/thread2938.asp (the one Graham Cole wrote). And I declare a variable for storing "delay count". Then , I could just change "delay count" by passing different parameter. Or I can call the major function that includes "delay function". This method seems doesn't work. Because when I call by constant (ex:NOPS(10)), it almost meet my require.But when I call by variable (ex:NOPS(delay_count) where delay_count = 10) it has serious overhead . It delays about (delay_count + 20~30) uS. Are there any more solutions ? Anyway , thank you all. I did learn a lot.

Read-Only Author Andrew Neil Posted 21-Jan-2005 07:54 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Andrew Neil "when I call by constant (ex:NOPS(10)), it almost meet my require.But when I call by variable (ex:NOPS(delay_count) where delay_count = 10) it has serious overhead ." See my post dated 11/17/03 15:26:56 in the thread I cited earlier: http://www.keil.com/forum/docs/thread2938.asp It specifically describes a way to cope with this overhead!

Read-Only Author Jon Ward Posted 21-Jan-2005 20:05 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Jon Ward That MACRO was originally written by me in the following thread: http://www.keil.com/forum/docs/thread1940.asp There, I made the following important note: NOTE: Do not use variables with this macro. Use constants only. Using a variable causes actual code to be generated for each ternary operator. Using constants causes the ternary operator to be evaluated by the preprocessor (which is what we want). Jon

Read-Only Author Jon Ward Posted 24-Jan-2005 05:31 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level Jon Ward OK - So, I used standard macros to create the same thing... NAME NOPS ?PR?NOPS?NOPS SEGMENT CODE RSEG ?PR?NOPS?NOPS NUMNOPS EQU 200 MakeNOP MACRO X PUBLIC NOPS_&X NOPS_&X: NOP ENDM NOP_LIST: REPT NUMNOPS MakeNOP %(NUMNOPS - ($ - NOP_LIST)) ENDM RET END Jon

Read-Only Author cui wei Posted 22-Jan-2005 08:51 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level cui wei sample: void delay_us(unsigned char counter) { ACC = 255 - counter; #pragma asm mov dptr,#DELAYBEGIN; jmp @a+dptr DELAYBEGIN: REPT (255 - 9) nop; ENDM #pragma endasm } note: counter must be from 9 to 255.

Read-Only Author erik malund Posted 24-Jan-2005 14:39 GMT Toolset C51	RE: How could I make a adjustable delay function in "micro-second" level erik malund #pragma asm Why on earth would you do that. Purt the subroutine in a .a51 module. also, the routine described is wrong ACC = 255 - counter; it should be ACC = 255 - counter - overhead jb acc.7,crash ; routine used for too short a delay Erik

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