Post by thread:[PIC]: >256 byte Table

Friends, I know this question has been asked, and yes I looked at the PICLIST FAQ. There was good info their, but I was hoping somebody could explain a few things to me. In MICROCHIPs application note AN556 "Implemeting a Table Read" the code is as follows: movlw LOW Table addwf offset movlw HIGH Table btfsc status,c addlw 1 movwf PCLATH movf offset,w call Table ; ; ; Table: movwf pcl retlw 'A' retlw 'B' retlw 'C' ; ; etc............ I know that "LOW" is taking the lower byte of "Table". Problem is,..... what is "Table"? Do you equate it to a number at the beginning of the program like: Table EQU H'0200' This will load 0x00 into "LOW" and 0x02 into "HIGH"? Does it have to have the same name as the table of data? Also, the register labeled "offset", is it some type of register that is being incremented, decremented,...etc? Thank you very much!! Best regards, Steve Steven Kosmerchock Radio Frequency Systems Phoenix Arizona USA http://www.rfsworld.com www.geocities.com/researchtriangle/lab/6584

Steve, 'TABLE' is a label. It is at the begining of the data table below. "OFFSET' is how deep into the table do you want to go. For instance, in the table listed below, lets say you had the offset at 2. In this case, RETLW would return "C". The reason for this is that at compile time, the compiler saw the label 'TABLE', and set it's address to whatever. This address can be found several places, but I like looking at the listing file. So when the table lookup routine is called, the PC is loaded with the address of the label table. Next it adds the 'OFFSET' to the PC to come up with the final destination address. And in this case, that equates to final destination address points to 'C' in the table. Is this clear to you now? Basically what you have is the compiler locates the table somewhere in memory, and the combination of the base address plus the offset equals the element in the table you want to retrieve. Hope this helps you out. Regards, Jim On Thu, 29 June 2000, "Kosmerchock, Steve" wrote: {Quote hidden}> > Friends, > > I know this question has been asked, and yes I looked at the > PICLIST FAQ. There was good info their, but I was hoping somebody could > explain a few things to me. > > In MICROCHIPs application note AN556 "Implemeting a Table Read" > the code is as follows: > > movlw LOW Table > addwf offset > movlw HIGH Table > btfsc status,c > addlw 1 > movwf PCLATH > movf offset,w > call Table > ; > ; > ; > Table: > movwf pcl > retlw 'A' > retlw 'B' > retlw 'C' > ; > ; > etc............ > > > I know that "LOW" is taking the lower byte of "Table". > Problem is,..... what is "Table"? Do you equate it to a > number at the beginning of the program like: > > Table EQU H'0200' > > This will load 0x00 into "LOW" and 0x02 into "HIGH"? > Does it have to have the same name as the table of data? > Also, the register labeled "offset", is it some type of > register that is being incremented, decremented,...etc? > > Thank you very much!! > > Best regards, > Steve > > > Steven Kosmerchock > Radio Frequency Systems > Phoenix Arizona USA > http://www.rfsworld.com > > http://www.geocities.com/researchtriangle/lab/6584 spam_OUTjimTakeThisOuTjpes.com

Hi You pretty much answer your own questions. I myself are not familiar with HIGH and LOW directives, so I looked in the Help file: 8.5.1 Syntax high <operand> low <operand> upper <operand> 8.5.2 Description These operators are used to return one byte of a multi-byte label value. This is done to handle dynamic pointer calculations as might be used with table read and write instructions. 8.5.3 Example movlw low size ; handle the lsb's movpf wreg, low size_lo movlw high size ; handle the msb's movpf wreg, high size_hi > I know that "LOW" is taking the lower byte of "Table". > Problem is,..... what is "Table"? Do you equate it to a > number at the beginning of the program like: > "Table" in this example is a constant (_L_iteral) which is the start address for your Table where you want to read the information from. This constant is derived from the Label "Table". When MPASM does its thing, it will do this: > Table EQU H'0200' If your Table sits at address H'0200", that is, (continue with your example, I would put an ORG H'0200' before "Table"). Then: > This will load 0x00 into "LOW" and 0x02 into "HIGH"? Yes. > Does it have to have the same name as the table of data? Yes, explained above, but not necessary. It could be any other constant. In this case it is used to find the start address of your table. > Also, the register labeled "offset", is it some type of > register that is being incremented, decremented,...etc? Yes, "Table" will be your start address, "offset" will be the ...erhm... offset from that start address to the value you want to read. So you load "offset" with the position/address for the value you want to read in the Table. Hope this helps Quentin

Guys..... I've used a number of tables that cover 1024 bytes. I like to locate the program in the first bank and the table in the second bank. I use the org directive to set the location of the table. Example.... (R=DEC) org 1024 Table movwf PCL fill (retlw HIBIT),56 org 1025+56 HL fill (retlw HLGT),9 fill (retlw HIBIT),19 org 1025+84 GT3 fill (retlw K3),10 etc Use org to set entries into the table Use fill to put in constants from that point Use the EQU to define those constants....if you want to change later and NOT retype the table. etc. You'll have to modify the info presented in the APP NOTE you mention to allow you to cover more than 256 entries (postions) into the table. Use HIGH Table and LOW Table. Hope that helps........ Phil Anderson..... On Thursday, June 29, 2000 10:19 AM, James Paul [SMTP:.....jimKILLspam@spam@JPES.COM] wrote: {Quote hidden}> Steve, > > 'TABLE' is a label. It is at the begining of the data table below. > "OFFSET' is how deep into the table do you want to go. > For instance, in the table listed below, lets say you had the offset > at 2. In this case, RETLW would return "C". > The reason for this is that at compile time, the compiler saw the > label 'TABLE', and set it's address to whatever. This address can > be found several places, but I like looking at the listing file. > So when the table lookup routine is called, the PC is loaded with > the address of the label table. Next it adds the 'OFFSET' to the PC > to come up with the final destination address. And in this case, > that equates to final destination address points to 'C' in the table. > Is this clear to you now? Basically what you have is the compiler > locates the table somewhere in memory, and the combination of the > base address plus the offset equals the element in the table you > want to retrieve. > > Hope this helps you out. > > > Regards, > > Jim > > > On Thu, 29 June 2000, "Kosmerchock, Steve" wrote: > > > > > Friends, > > > > I know this question has been asked, and yes I looked at the > > PICLIST FAQ. There was good info their, but I was hoping somebody could > > explain a few things to me. > > > > In MICROCHIPs application note AN556 "Implemeting a Table Read" > > the code is as follows: > > > > movlw LOW Table > > addwf offset > > movlw HIGH Table > > btfsc status,c > > addlw 1 > > movwf PCLATH > > movf offset,w > > call Table > > ; > > ; > > ; > > Table: > > movwf pcl > > retlw 'A' > > retlw 'B' > > retlw 'C' > > ; > > ; > > etc............ > > > > > > I know that "LOW" is taking the lower byte of "Table". > > Problem is,..... what is "Table"? Do you equate it to a > > number at the beginning of the program like: > > > > Table EQU H'0200' > > > > This will load 0x00 into "LOW" and 0x02 into "HIGH"? > > Does it have to have the same name as the table of data? > > Also, the register labeled "offset", is it some type of > > register that is being incremented, decremented,...etc? > > > > Thank you very much!! > > > > Best regards, > > Steve > > > > > > Steven Kosmerchock > > Radio Frequency Systems > > Phoenix Arizona USA > > http://www.rfsworld.com > > > > http://www.geocities.com/researchtriangle/lab/6584 > > jimKILLspamjpes.com

I made a mistake with some code I posted yesterday and is ammended below. Table can access 1 to 8178 bytes (assuming max ROM of 8K) Table movlw High(TStart) movwf PCLATH movf OffsetH,W addwf PCLATH movlw Low(TStart) addwf OffsetL,W btfsc STATUS,C incf PCLATH movf OffsetL,W call DoTable movlw High(here) movwf PCLATH ; reset PCLATH here goto here org 0x???? DoTable addwf PCL TStart Retlw d'0' etc As an example of how to use it, say you want to output speech data at 5K samples per second. A simple R2R ladder is on PortB. The speech table has 3000 data points Start clrf OffsetH clrf OffsetL SoundLoop ; 200uS loop time = 5000 samples per second movlw High(Table) movwf PCLATH call Table ; get sound data movwf PORTB movlw High(here) movwf PCLATH ; reset PCLATH here incf OffsetL ; add 1 to data pointer btfsc STATUS,C incf OffsetH NoUp movlw Low(d'3000') xorwf OffsetL,W btfss STATUS,Z goto SoundLoop movlw High(d'3000') xorwf OffsetH,W btfss STATUS,Z goto SoundLoop goto Start ; ; SOUND DATA TABLE 3000 ELEMENTS ; Table movlw High(TStart) movwf PCLATH movf OffsetH,W addwf PCLATH movlw Low(TStart) addwf OffsetL,W btfsc STATUS,C incf PCLATH movf OffsetL,W DoTable addwf PCL TStart DT "Hello. I'm Mr Ed" ; plus another 2984 data points end PS: the text won't sound like that coming from PORTB ;-) PPS if you want an easy way to create a 3000 point data table ready for MPASM see http://www.picnpoke.com/demo/dtimg.html -- Best regards Tony http://www.picnpoke.com .....salesKILLspam.....picnpoke.com

Hi Tony. AFAIK it can be done in more straight way. call Dispatcher ; will be returned here Dispatcher: movlw High TStart addwf OffsetH,W movwf PCLATH movlw Low TStart addwf OffsetL,W skpnc incf PCLATH,F movwf PCL ;computed goto with right PCLATH TStart: dt data0,data1,data2,... ;retlw's WBR Dmitry. {Quote hidden}> Table can access 1 to 8178 bytes (assuming max ROM of 8K) > > Table movlw High(TStart) > movwf PCLATH > movf OffsetH,W > addwf PCLATH > movlw Low(TStart) > addwf OffsetL,W > btfsc STATUS,C > incf PCLATH > > movf OffsetL,W > call DoTable > > movlw High(here) > movwf PCLATH ; reset PCLATH > > here goto here > > org 0x???? > > DoTable addwf PCL > TStart Retlw d'0' > etc > > As an example of how to use it, say you want to output speech data at 5K > samples per second. > A simple R2R ladder is on PortB. > The speech table has 3000 data points > > Start clrf OffsetH > clrf OffsetL > > SoundLoop ; 200uS loop time = 5000 samples per second > > movlw High(Table) > movwf PCLATH > call Table ; get sound data > movwf PORTB > > movlw High(here) > movwf PCLATH ; reset PCLATH > > here incf OffsetL ; add 1 to data pointer > btfsc STATUS,C > incf OffsetH > > NoUp movlw Low(d'3000') > xorwf OffsetL,W > btfss STATUS,Z > goto SoundLoop > > movlw High(d'3000') > xorwf OffsetH,W > btfss STATUS,Z > goto SoundLoop > goto Start > ; > ; SOUND DATA TABLE 3000 ELEMENTS > ; > Table movlw High(TStart) > movwf PCLATH > movf OffsetH,W > addwf PCLATH > movlw Low(TStart) > addwf OffsetL,W > btfsc STATUS,C > incf PCLATH > > movf OffsetL,W > DoTable addwf PCL > TStart DT "Hello. I'm Mr Ed" > > ; plus another 2984 data points > > end > > PS: the text won't sound like that coming from PORTB ;-) > > PPS if you want an easy way to create a 3000 point data table ready for > MPASM see > > http://www.picnpoke.com/demo/dtimg.html > > -- > Best regards > > Tony > > http://www.picnpoke.com > EraseMEsalesspam_OUTTakeThisOuTpicnpoke.com

On Fri, 30 Jun 2000, Dmitry Kiryashov wrote: {Quote hidden}> Hi Tony. > > AFAIK it can be done in more straight way. > > call Dispatcher > ; will be returned here > > > Dispatcher: > movlw High TStart > addwf OffsetH,W > movwf PCLATH > > movlw Low TStart > addwf OffsetL,W > skpnc > incf PCLATH,F > > movwf PCL ;computed goto with right PCLATH > > TStart: > dt data0,data1,data2,... ;retlw's > > WBR Dmitry. And if you look closely, this IS 12 instructions! I agree with you, Dmitry. This is the better way of doing it (and it's been posted here several times before [and James probably has it stuffed down in one of his web pages]). Incidently, since we are talking about 18cxxx parts too, there are several ways this code could be implemented. It could be left as is... But the table read and writes allow you to pack the 8 bit data values into program memory more efficiently. That is, the 14bit core data tables have 6-bits for the RETLW instruction. movlw LOW TStart addwf OffsetL,w movwf tabptrl,a movlw HIGH TStart addwc OffsetH,w movwf tabptrh,a clrf tabptru,a At this point, you can issue any table read instruction and get access to the data. If you're accessing consecutive entries in the table then you could do this: tblrd *+ movf tablat,w,a Successive accesses now don't have to go through the long part of initializing the table pointer. Scott

Alice Campbell wrote: > > Hi Tony, > > I laughing! ive been mulling for a while a little marble- > sized thingie that consists of an 8-pin smd pic, tiny > microphone, and thermal switch that you rig up to screech > (once) when hot coffee is poured on it in a mug.... > and having the ability to have my IDE play blatting noises at > me, what a concept.... > thanks, > > alice Hi Alice, Make sure you don't swallow it. It might make an awful scary sound coming out the other end. On Fri, 30 Jun 2000, Dmitry Kiryashov wrote: > Hi Tony. > > AFAIK it can be done in more straight way. It sure can - I'll remember it this time ;-) -- Best regards Tony http://www.picnpoke.com salesspam_OUTpicnpoke.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

> Alice Campbell wrote: > > > > Hi Tony, > > > > I laughing! ive been mulling for a while a little marble- > > sized thingie that consists of an 8-pin smd pic, tiny > > microphone, and thermal switch that you rig up to screech > > (once) when hot coffee is poured on it in a mug.... > > and having the ability to have my IDE play blatting noises at > > me, what a concept.... > > thanks, > > > > alice > > Hi Alice, > > Make sure you don't swallow it. It might make an awful scary sound > coming out the other end. Er, WHAT/WHO ? will be making the awful scary sound ? -- 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

Jinx wrote: {Quote hidden}> > > Alice Campbell wrote: > > > > > > Hi Tony, > > > > > > I laughing! ive been mulling for a while a little marble- > > > sized thingie that consists of an 8-pin smd pic, tiny > > > microphone, and thermal switch that you rig up to screech > > > (once) when hot coffee is poured on it in a mug.... > > > and having the ability to have my IDE play blatting noises at > > > me, what a concept.... > > > thanks, > > > > > > alice > > > > Hi Alice, > > > > Make sure you don't swallow it. It might make an awful scary sound > > coming out the other end. > > Er, WHAT/WHO ? will be making the awful scary sound ? > > -- > 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 The little marble sized thingy! -- Best regards Tony http://www.picnpoke.com @spam@salesKILLspampicnpoke.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