PIC18F8527 Array Limit

[jtowich]

According to the PBP manual, PIC18Xxxxx device variable arrays are only limited by available memory. I have verified there is lots of available memory, but the line:

AIAvgReg var word[128]

gets me this error

ERROR: Unable to fit variable AIAvgReg

Reducing the number of elements to 127 works ok. Even if the limit was one RAM bank, as in older PICS, the 128 Words should still fit in one bank.

Any idea what is wrong?

PBP 2.60A, PBPL

[ScaleRobotics]

Any idea what is wrong?

PBP 2.60A, PBPL

No, but it does compile correctly here for
AIAvgReg var word[1500], even when using pbpl.

So, either, you are using too many other variables, or possibly, you are compiling for the wrong chip. Or, maybe mpasm version issue?

Walter

[HenrikOlsson]

Hi,
What else do you have in ways of variables? I tried it here and it compiles just fine, even with the array declared as 1900 words. Are you sure you're compiling for the 18F8527 and not a device with less RAM?

/Henrik.

EDIT: Ha, double post there Walter, pretty identical as well :-)

[jtowich]

Thanks for the quick response

I am definitely have the 18F8527 selected. I tried an array of 1000 words and it didn't work. However, it works fine if I try 10 arrays of 127 words, so lack of memory is not an issue. Just doesn't like anything over 255 bytes in an array.

I'll keep looking.

[ScaleRobotics]

If you open up your xxxx.lst file, you can see where your assembler thinks the ram start and end locations are. For some reason, this sounds buggered. It also will show which MPASM version you are using, and which processor includes you are using.

Here's what mine looked like. You can compare it to yours and see if there are differences in RAM locations.


MPASM 5.38 UNTITLED.ASM 1-21-2011 10:05:20 PAGE 1


LOC OBJECT CODE LINE SOURCE TEXT
VALUE

00001
00002 ; PICBASIC PRO(TM) Compiler 2.60LA, (c) 1998, 2009 microEngineering Labs, Inc. All Rights Reserved.
00000001 00003 _USED EQU 1
00004
00005 INCLUDE "C:\PBP\18F8527.INC"
00001 ;************************************************* ***************
00002 ;* 18F8527.INC *
00003 ;* *
00004 ;* By : Leonard Zerman, Jeff Schmoyer *
00005 ;* Notice : Copyright (c) 2008 microEngineering Labs, Inc. *
00006 ;* All Rights Reserved *
00007 ;* Date : 09/15/08 *
00008 ;* Version : 2.60 *
00009 ;* Notes : *
00010 ;************************************************* ***************
00017 LIST
00018 LIST p = 18F8527, r = dec, w = -311, w = -230, f = inhx32
00019 INCLUDE "P18F8527.INC" ; MPASM Header
00001 LIST
00002
00003 ;================================================= =========================
00004 ; MPASM PIC18F8527 processor include
00005 ;
00006 ; (c) Copyright 1999-2010 Microchip Technology, All rights reserved
00007 ;================================================= =========================
00008
02400 LIST
300000 32FF 00020 __CONFIG _CONFIG1H, _OSC_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
300002 F31F 00021 __CONFIG _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
300006 FF8B 00022 __CONFIG _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _BBSIZ_BB2K_4L & _XINST_OFF_4L
00025 LIST
00F00000 00026 EEPROM_START EQU 0F00000h
00000040 00027 BLOCK_SIZE EQU 64
00006
00000000 00007 RAM_START EQU 00000h
00000F5F 00008 RAM_END EQU 00F5Fh
00000010 00009 RAM_BANKS EQU 00010h
00000060 00010 BANK0_START EQU 00060h
000000FF 00011 BANK0_END EQU 000FFh
00000100 00012 BANK1_START EQU 00100h
000001FF 00013 BANK1_END EQU 001FFh
00000200 00014 BANK2_START EQU 00200h
000002FF 00015 BANK2_END EQU 002FFh
00000300 00016 BANK3_START EQU 00300h
000003FF 00017 BANK3_END EQU 003FFh
00000400 00018 BANK4_START EQU 00400h
000004FF 00019 BANK4_END EQU 004FFh
00000500 00020 BANK5_START EQU 00500h
000005FF 00021 BANK5_END EQU 005FFh
00000600 00022 BANK6_START EQU 00600h
000006FF 00023 BANK6_END EQU 006FFh
00000700 00024 BANK7_START EQU 00700h
000007FF 00025 BANK7_END EQU 007FFh
MPASM 5.38 UNTITLED.ASM 1-21-2011 10:05:20 PAGE 2


LOC OBJECT CODE LINE SOURCE TEXT
VALUE

00000800 00026 BANK8_START EQU 00800h
000008FF 00027 BANK8_END EQU 008FFh
00000900 00028 BANK9_START EQU 00900h
000009FF 00029 BANK9_END EQU 009FFh
00000A00 00030 BANK10_START EQU 00A00h
00000AFF 00031 BANK10_END EQU 00AFFh
00000B00 00032 BANK11_START EQU 00B00h
00000BFF 00033 BANK11_END EQU 00BFFh
00000C00 00034 BANK12_START EQU 00C00h
00000CFF 00035 BANK12_END EQU 00CFFh
00000D00 00036 BANK13_START EQU 00D00h
00000DFF 00037 BANK13_END EQU 00DFFh
00000E00 00038 BANK14_START EQU 00E00h
00000EFF 00039 BANK14_END EQU 00EFFh
00000F00 00040 BANK15_START EQU 00F00h
00000F5F 00041 BANK15_END EQU 00F5Fh
00000000 00042 BANKA_START EQU 00000h
0000005F 00043 BANKA_END EQU 0005Fh

[jtowich]

My lst shows the same memory locations and processor. Strange.


00001
00002 ; PICBASIC PRO(TM) Compiler 2.60LA, (c) 1998, 2009 microEngineering Labs, Inc. All Rights Reserved.
00000001 00003 _USED EQU 1
00004
00005 INCLUDE "C:\PBP\18F8527.INC"
00001 ;************************************************* ***************
00002 ;* 18F8527.INC *
00003 ;* *
00004 ;* By : Leonard Zerman, Jeff Schmoyer *
00005 ;* Notice : Copyright (c) 2008 microEngineering Labs, Inc. *
00006 ;* All Rights Reserved *
00007 ;* Date : 09/15/08 *
00008 ;* Version : 2.60 *
00009 ;* Notes : *
00010 ;************************************************* ***************
00017 LIST
00018 LIST p = 18F8527, r = dec, w = -311, w = -230, f = inhx32
00019 INCLUDE "P18F8527.INC" ; MPASM Header
00001 LIST
00002
00003 ;================================================= =========================
00004 ; $Id: P18F8527.INC,v 1.2.2.3 2005/10/18 21:44:56 curtiss Exp $
00005 ; MPASM PIC18F8527 processor include
00006 ;
00007 ; (c) Copyright 1999-2005 Microchip Technology, All rights reserved
00008 ;================================================= =========================



00000000 00029 RAM_START EQU 00000h
00000F5F 00030 RAM_END EQU 00F5Fh
00000010 00031 RAM_BANKS EQU 00010h
00000060 00032 BANK0_START EQU 00060h
000000FF 00033 BANK0_END EQU 000FFh
00000100 00034 BANK1_START EQU 00100h
000001FF 00035 BANK1_END EQU 001FFh
00000200 00036 BANK2_START EQU 00200h
000002FF 00037 BANK2_END EQU 002FFh
00000300 00038 BANK3_START EQU 00300h
000003FF 00039 BANK3_END EQU 003FFh
00000400 00040 BANK4_START EQU 00400h
000004FF 00041 BANK4_END EQU 004FFh
00000500 00042 BANK5_START EQU 00500h
000005FF 00043 BANK5_END EQU 005FFh
00000600 00044 BANK6_START EQU 00600h
000006FF 00045 BANK6_END EQU 006FFh
00000700 00046 BANK7_START EQU 00700h
000007FF 00047 BANK7_END EQU 007FFh
00000800 00048 BANK8_START EQU 00800h
000008FF 00049 BANK8_END EQU 008FFh
00000900 00050 BANK9_START EQU 00900h
000009FF 00051 BANK9_END EQU 009FFh
00000A00 00052 BANK10_START EQU 00A00h
00000AFF 00053 BANK10_END EQU 00AFFh
00000B00 00054 BANK11_START EQU 00B00h
00000BFF 00055 BANK11_END EQU 00BFFh
00000C00 00056 BANK12_START EQU 00C00h
00000CFF 00057 BANK12_END EQU 00CFFh
00000D00 00058 BANK13_START EQU 00D00h
00000DFF 00059 BANK13_END EQU 00DFFh
00000E00 00060 BANK14_START EQU 00E00h
00000EFF 00061 BANK14_END EQU 00EFFh
00000F00 00062 BANK15_START EQU 00F00h
00000F5F 00063 BANK15_END EQU 00F5Fh
00000000 00064 BANKA_START EQU 00000h
0000005F 00065 BANKA_END EQU 0005Fh
00066
00000000 00067 FLAGS EQU RAM_START + 000h
00000001 00068 GOP EQU RAM_START + 001h
MPASM 5.03 PCB6AI~1.ASM 1-21-2011 12:16:16 PAGE 3

[ScaleRobotics]

Just a guess, but I suspect an MPLAB upgrade will fix your problem.



MPASM 5.03


is pretty old....

I suspect that whatever is wrong, is fixed in one of the many newer versions.

[jtowich]

upgraded to MPASM 5.39, no change.

I'll try reloading all the software when I get a chance.

[jtowich]

I found the problem.

I am using assembly interrupts that reserve a location in each bank for the wsave register. This effectively limits an array size to 255 bytes since the array can't cross this reserved register.

Luckily this processor has a special stack that will store the W, STATUS, and BSR registers automatically and then automatically restore them if a "fast" retfie command is used. This removes the requirement to reserve a memory location in each bank for the wsave register. Using this method works as advertised. This will only work if high priority interrupts are not used, which was the case in my code.

[Bruce]

On 18F types you can force your context saving vars to be placed in access ram so there's no need to put them in more than 1 place.

wsave var byte BANKA SYSTEM ' location for WREG
ssave var byte BANKA SYSTEM ' location for STATUS register
bsave var byte BANKA SYSTEM ' location for BSR register

[ScaleRobotics]

I found the problem.

I am using assembly interrupts that reserve a location in each bank for the wsave register. This effectively limits an array size to 255 bytes since the array can't cross this reserved register.


You might want to use DT_INTS, it makes it pretty easy to use interrupts, and doesn't cause the problems you are seeing, whether using asm or pbp type interrupts.

http://darreltaylor.com/DT_INTS-18/home.html