Post by thread:[PIC]: Compares and Delays

Piecing together a small app to test my PICs (PIC16F876) The first thing I noticed is that the architecture does not support branch by compare in favor of a skip type instruction. Similar to: movlw 'Z' ; ASCII compare value movwf B ; load b with "compare to" value movlw A ; move test (A) to w for work sublw B ; sub B compare value from w btfsc STATUS, Z ; if not zero, skip goto goto ZeroIsSet Is there a way to do these compares in less instructions if one knows what value will be compared against ahead of time? Just comparing to a set of three single character ASCII values in upper case. Sort of like a case statement, but can just flow over into other cases sequentially. Secondly I wanted to insert a delay into the bit of code below in lieu of external stimulus to make sure my PIC is functional. The goal would be to get a blinking delay around a second. I know this is relatively simple but examples I have found are in picbasic so delay structure is done with a single command. Still trying to wrap my brain around the instruction set as it differs wildly from the M8k and HC-11. Running at 4Mhz and any sort of "hello world" style program will do. Thanks! P.S. Incidentally, anyone living in the Northern VA area around Warrenton or such........there is a Radio Shack going out of business on Route 17 near Bealeton and all components are 50-75% off including transformers and motors. Code Below: //========================================== org 0 nop bsf PORTB, 0 ; Set PORTB.0 low bsf STATUS, RP0 bcf TRISB ^ 0x080, 0 ; PORTB.0 set as output bcf STATUS, RP0 Loop movf PORTA, w ; xfer PORTA.0 to PORTB.0 movwf PORTB goto Loop end _________________________________________________________________ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Branch_true movlw .3 ; get test value subwf fcn_set,w ; test register leaving result in w (w is trashed) btfsc STATUS,Z ; see if true goto next_segment ; then branch to new location And the next bit delays movlw .xx ; delay value call short ; or long or extra_long for 8,16,24 bit periods I keep the following code in a section called "Timer.inc" and call this at the top of a program the Delay xx requires processor speed to be defined "CLOCK_RATE EQU 4000000 ; CRYSTAL IS 4.00 MHZ" to calculate corect delays I believe this macro was by origanally Robin Abbot (it was in EPE about three years ago). Regards Steve... ;------------------ DELAY ROUTINE: UNERVISAL ------------ DELAY2 NOP ; PACKING SPACES FOR EXACT DELAYS DELAY1 NOP ; SHORT ; THE TIMER MODULE IF DEBUG == 1 ; TEST DEBUG FLAG AND WRITE AROUND RETLW 0 ; QUICK EXIT IF DEBUG ELSE ; MOVWF TIMER ; LOAD WITH CONTENTS OF W REG DECFSZ TIMER,F ; DEC TIMER GOTO $-1 ; IF CONTENTS OF TIMER IS NOT 0, GO BACK 1 LINE ENDIF ; PUT IN TIMER DELAY4 RETLW 0 ; RETURN LONG IF DEBUG == 1 ; TEST DEBUG FLAG AND WRITE AROUND RETLW 0 ; QUICK EXIT IF DEBUG ELSE ; MOVWF GP1 ; SUPLEMENTRY COUNTER MOVLW 0XF0 ; VALUE FOR SHORT CALL SHORT ; DO SHORT AS WELL DECFSZ GP1,F ; DECREASE SUPLEMENTRY COUNTER GOTO $-3 ; AGAIN TIL FINISHED RETLW 0 ; EXIT ENDIF ; PUT IN TIMER EXTRA_LONG IF DEBUG == 1 ; TEST DEBUG FLAG AND WRITE AROUND RETLW 0 ; QUICK EXIT IF DEBUG ELSE MOVWF GP2 ; SECOND ORDER COUNTER EXLNG_1 MOVLW .255 ; VALUE FOR LONG CALL LONG ; DO IT DECFSZ GP2,F ; REDUCE SECOND ORDER COUNTER GOTO EXLNG_1 ; DO MORE RETLW 0 ENDIF ;-----------THIS MACRO MAKES EXACT DELAYS FROM 0 TO 186420 INSTRUCTIONS------ DELAY macro Cyc LOCAL Nx SmallCyc=Cyc IF (SmallCyc<8) IF (SmallCyc&1) NOP SmallCyc-=1 ENDIF WHILE (SmallCyc>=4) CALL DELAY4 SmallCyc-=4 ENDW IF (SmallCyc==2) GOTO NX NX: SmallCyc-=2 ENDIF ENDIF IF Cyc>.775 BIGCyc=(Cyc-.730) LoopDelay=BIGCYC/.728 MOVLW LOOPDELAY+1 CALL LONG SMALLCYC=CYC-(.730+LoopDelay*.728+3) ENDIF IF(SmallCyc) LoopDelay=(SmallCyc-3)-5 MOVLW LoopDelay/3+1 CALL SHORT-LoopDelay%3 ENDIF ENDM Notes: Debug equ .0 ; or .1 if the delay is not required Timer is a memory location GP1 is another memory location GP2 is another memory location {Original Message removed}

Robert O'Robberson <spam_OUTPICLISTTakeThisOuTmitvma.mit.edu> wrote: > movlw 'Z' ; ASCII compare value > movwf B ; load b with "compare to" value > movlw A ; move test (A) to w for work > sublw B ; sub B compare value from w > btfsc STATUS, Z ; if not zero, skip goto > goto ZeroIsSet > > Is there a way to do these compares in less instructions if one > knows what value will be compared against ahead of time? Just > comparing to a set of three single character ASCII values in upper > case. Sort of like a case statement, but can just flow over into > other cases sequentially. Robert: MOVF A,W ;W HOLDS THE CHARACTER. XORWF 'X',W ;CHARACTER = "X"? BZ ITISX ;IF SO, JUMP. XORWF 'Y'^'X',W ;OTHERWISE, CHARACTER = "Y"? BZ ITISY ;IF SO, JUMP. XORWF 'Z'^'Y',W ;OTHERWISE, CHARACTER = "Z"? BZ ITISZ ;IF SO, JUMP. GOTO DEFAULT ;OTHERWISE, IT'S NONE OF THE ABOVE. Before you ask, "BZ" is a pseudo-op that means "Branch if Zero"; it's documented in the MPASM User's Manual. "BZ LABEL" assembles to "BTFSC STATUS,Z / GOTO LABEL". > Secondly I wanted to insert a delay into the bit of code below in > lieu of external stimulus to make sure my PIC is functional. The > goal would be to get a blinking delay around a second. .... Running > at 4Mhz and any sort of "hello world" style program will do. MSTMR EQU [ANY REGISTER] MSTMR2 EQU [ANOTHER REGISTER] .... MOVLW 250 CALL WAITMS MOVLW 250 CALL WAITMS MOVLW 250 CALL WAITMS MOVLW 250 CALL WAITMS .... ; DELAY APPROXIMATELY X MILLISECONDS (4MHZ CLOCK). ENTER WITH ; NUMBER OF MILLISECONDS IN W (0 = 256). WAITMS: MOVWF MSTMR ;1-MSTMR = # OF MILLISECONDS. WAITMS1: MOVLW 248 ;2-SETUP TO WAIT 1 MILLISECOND. MOVWF MSTMR2 ; WAITMS2: NOP ;248-WASTE A CYCLE. THIS COULD ; ALSO BE A "CLRWDT". DECFSZ MSTMR2 ;743- GOTO WAITMS2 ; DECFSZ MSTMR ;3*MSTMR-1 -HAVE WE WAITED LONG ; ENOUGH? GOTO WAITMS1 ; IF NOT, LOOP BACK. RETLW 0 ;2-OTHERWISE, RETURN. -Andy === Andrew Warren -- .....aiwKILLspam@spam@cypress.com === Principal Design Engineer === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> The first thing I noticed is that the architecture does not > support branch by compare in favor of a skip type instruction. > Similar to: > > movlw 'Z' ; ASCII compare value > movwf B ; load b with "compare to" value > movlw A ; move test (A) to w for work > sublw B ; sub B compare value from w > btfsc STATUS, Z ; if not zero, skip goto > goto ZeroIsSet True, there are no conditional branch instructions, but this is a cumbersome way to test whether the value at A is "Z". A more reasonable method is: movf a, w ;get the value to check sublw 'z' ;compare to "z" skip_z ;is it "z" goto not_z ;no ; ; The value in A is "z". ; SKIP_Z is one of my macros that just expands to BTFSS STATUS, Z on the 16 family. I have several SKIP_xxx macros because they make the code easier to read and avoid the need to think about which way the carry flag gets set on a subtract and the fact that W is subtracted from the file register or literal instead of the other way around. The SKIP_WLE (skip if W was less than or equal to) and SKIP_WGT (skip if W was greater than) macros in particular save a lot of figuring it out all over again each time. These and other macros are available in STD.INS.ASPIC at http://www.embedinc.com/pic. Note that the PIC 18 family does have some conditional branch instructions. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> -----Original Message----- > From: Olin Lathrop [SMTP:olin_piclistKILLspamEMBEDINC.COM] > Sent: Saturday, March 29, 2003 9:18 PM > To: .....PICLISTKILLspam.....MITVMA.MIT.EDU > Subject: Re: [PIC]: Compares and Delays > > > SKIP_Z is one of my macros that just expands to BTFSS STATUS, Z on the 16 > family. > > Not wishing to be rude, but MPASM already has skpz and skpnz macro's. Why not use the macro's that come with the tool? (i.e. the ones that other people will already be using). Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to EraseMEpostmasterspam_OUTTakeThisOuTbookham.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> -----Original Message----- > From: Reinaldo Alvares [SMTP:RemoveMEreinaldoalvaresTakeThisOuTTELIA.COM] > Sent: Monday, March 31, 2003 8:30 AM > To: spamBeGonePICLISTspamBeGoneMITVMA.MIT.EDU > Subject: Re: [PIC]: Compares and Delays > > By the way, Do you know why MPLAB 6 shows "skpz" and "skpnz" in red > meaning > BAD? > They compile properly and simulate properly too, but the red color makes > me > feel uncomfortable! > Regards > RA > What version are you using? 6.13 seems to colour all the standard macro instructions properly. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to TakeThisOuTpostmasterEraseMEspam_OUTbookham.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> By the way, Do you know why MPLAB 6 shows "skpz" and "skpnz" > in red meaning BAD? You can change colours using Edit/Properties. Make BAD the same as GOOD if you like > They compile properly and simulate properly too, but the red color > makes me feel uncomfortable! > Regards > RA I think I'd trade a little discomfort for a successful compile. There are times when maybe you'd want your attention drawn to a pseudo- opcode like bnz that compiles to two instructions if space or timing is important -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservEraseMEEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

>> SKIP_Z is one of my macros that just expands to BTFSS STATUS, Z on the >> 16 >> family. >> >> > Not wishing to be rude, but MPASM already has skpz and skpnz macro's. > Why > not use the macro's that come with the tool? (i.e. the ones that other > people will already be using). I wrote mine before MPASM had these, or at least before I heard about them. I know people have mentioned them here, but I still can't find any reference to them in the latest "MPASM User's Guide with MPLINK and MPLIB" (DS33014G). I feel uncomfortable using features that are not documented. In any case, I've got way too much existing code to change now. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservspam_OUTKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Mon, 31 Mar 2003, Olin Lathrop wrote: > >> SKIP_Z is one of my macros that just expands to BTFSS STATUS, Z on the > >> 16 > >> family. > >> > >> > > Not wishing to be rude, but MPASM already has skpz and skpnz macro's. > > Why > > not use the macro's that come with the tool? (i.e. the ones that other > > people will already be using). > > I wrote mine before MPASM had these, or at least before I heard about > them. I know people have mentioned them here, but I still can't find any > reference to them in the latest "MPASM User's Guide with MPLINK and MPLIB" > (DS33014G). I feel uncomfortable using features that are not documented. > In any case, I've got way too much existing code to change now. When comparing hex files for MPASM and gpasm I was surprised to discover that the SKPXX macros were not supported for 18F family in the versions of MPASM distributed with pre 6.0 MPLAB. In the pass, I've seen the macros defined in two places: the "MPASM and MPLINK PICmicro Quick Reference Guide" (DS30400E) and in the MPASM help under MPLAB. In the reference guide, the macros are described in the section titled "12-bit/14-bit Core Special Instruction Mnemonics". Conspicuously absent is '16-bit'. AFAICT, the macros are intentionally not defined for the 16-bit cores. I doubt this fact is mentioned in the 14-bit to 16-bit transition guide. When it's important for me to have source that can be assembled by gpasm and MPASM, I added this to my Makefile: # gpasm programs ASM = gpasm --define GPASM=1 Later on I have this: $(PROJECT).cod: $(SOURCES) $(ASM) $(PROJECT).asm In the source, I have this: ifndef GPASM MESSG "defining standard macros for MPASM" include "mpasm.inc" endif The mpasm.inc file looks like this: ================================================================== ;sigh... What was microchip thinking. Mpasm for the 18f parts no ;longer includes the common macros: CLRC macro BCF STATUS,C endm SKPNC macro BTFSC STATUS,C endm SKPC macro BTFSS STATUS,C endm SETZ macro BSF STATUS,Z endm CLRZ macro BCF STATUS,Z endm SKPZ macro BTFSS STATUS,Z endm SKPNZ macro BTFSC STATUS,Z endm SKPDC macro BTFSS STATUS,DC endm SKPNDC macro BTFSC STATUS,DC endm ================================================================== Scott -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body

Olin Lathrop <EraseMEPICLISTspamspamBeGonemitvma.mit.edu> wrote: > > Not wishing to be rude, but MPASM already has skpz and skpnz > > macro's. Why not use the macro's that come with the tool? (i.e. > > the ones that other people will already be using). > > I wrote mine before MPASM had these, or at least before I heard > about them. They've been in the Microchip assembler since long before it was even called MPASM. > I know people have mentioned them here, but I still can't find any > reference to them in the latest "MPASM User's Guide with MPLINK and > MPLIB" (DS33014G). Look harder. They're documented in Table B.11, on page 185. They're also documented in the MPASM.HLP file; click Instruction Sets, 12-Bit Core Instruction Set, 12-Bit/14-Bit Core Special Instruction Mnemonics. -Andy === Andrew Warren -- RemoveMEaiwKILLspamcypress.com === Principal Design Engineer === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservSTOPspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> Look harder. They're documented in Table B.11, on page 185. Thanks, I never noticed that table before. I wasn't expecting new information to be in a "Quick Reference" section. I've always used the PIC data sheet for the instruction reference. It's also interesting to note that LCALL and LGOTO are only listed but their description is missing. It again doesn't make me feel comfortable about using them. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservSTOPspamEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

On Tuesday, Apr 1, 2003, at 09:11 Australia/Sydney, Olin Lathrop wrote: >> Look harder. They're documented in Table B.11, on page 185. > > Thanks, I never noticed that table before. I wasn't expecting new > information to be in a "Quick Reference" section. I've always used the > PIC data sheet for the instruction reference. It's also interesting to > note that LCALL and LGOTO are only listed but their description is > missing. It again doesn't make me feel comfortable about using them. You didn't learn something from the list did you Olin? :-) Just curious, as it is April 1st down here after all! Sean - Running back down into my bunker! -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Careful u will b olinized..................................... (l@@k loadz a periodz) -----Original Message----- From: pic microcontroller discussion list [EraseMEPICLISTEraseMEMITVMA.MIT.EDU] On Behalf Of Sean Alcorn - PIC Stuff Sent: 01 April 2003 00:24 To: @spam@PICLIST@spam@spam_OUTMITVMA.MIT.EDU Subject: Re: [PIC]: Compares and Delays On Tuesday, Apr 1, 2003, at 09:11 Australia/Sydney, Olin Lathrop wrote: >> Look harder. They're documented in Table B.11, on page 185. > > Thanks, I never noticed that table before. I wasn't expecting new > information to be in a "Quick Reference" section. I've always used > the PIC data sheet for the instruction reference. It's also > interesting to note that LCALL and LGOTO are only listed but their > description is missing. It again doesn't make me feel comfortable > about using them. You didn't learn something from the list did you Olin? :-) Just curious, as it is April 1st down here after all! Sean - Running back down into my bunker! -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestspam_OUTmitvma.mit.edu>