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Specifying configuration bit settings in PICBASIC PRO™ programs.
It is possible to add a line to your PICBASIC PRO™ program that will place configuration bit settings in the generated hex file. The method used depends on the assembler that you are using in conjunction with PBP. By default, the compiler calls its built-in assembler, PM.EXE.
If you are compiling for 18C or 18F PICs, you must use the Microchip
assembler, MPASMWIN.EXE. Some Windows interface software will specify
MPASMWIN as the default assembler for all the PICs.
The easiest way to know what assembler is in use is to do a compile. If you see the MPASM window pop up momentarily and display a green progress bar, you are using MPASMWIN and should follow the appropriate procedure below. If no popup window appears, you are using PM.
If you add a configuration directive to your program file, you are actually replacing the default configuration that the compiler would otherwise include. The easiest way to determine the correct syntax is to get examples from the compiler and assembler's built-in resource files. To that end, it's best to understand how the compiler determines the config defaults.
When PICBASIC PRO is invoked, whether through a Windows interface or DOS command line, it is given a set of parameters that tell it how to proceed. To determine the configuration defaults, it needs to know which PICmicro® is being used and which assembler to use.
The first thing the compiler looks for is a file in the PBP folder that matches the targeted PIC®. If you tell it to compile for a 16F84A, it reads the file "16F84A.INC". The contents of this file are divided into 2 sections, one for each assembler. An internal variable, "PM_USED", tells the compiler which section of the file to use. In the following example, you will see that the top section ("ifdef" to "else") is meant for the PM assembler and the bottom section ("else" to "endif") is meant for the MPASM assembler.
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ifdef PM_USED
LIST
include 'M16F8x.INC' ; PM header
device pic16F84A, xt_osc, wdt_on, protect_off
XALL
NOLIST
else
LIST
LIST p = 16F84A, r = dec, w = -302
INCLUDE "P16F84A.INC" ; MPASM Header
__config _XT_OSC & _WDT_ON & _CP_OFF
NOLIST
endif
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For each assembler, PBP is given a header file and a set of defaults. The header file is important because it holds the definitions of the labels used to set the configuration. Keep in mind that the labels in MPASMWIN are case-sensitive, in PM they are not.
Procedure for PM.EXE:
Let's go through an example. Let's say we want to compile for the 16F877 using PM and we want to set the oscillator configuration to HS and enable code protection. Assuming the compiler is installed at C:\PBP, we view the file C:\PBP\16F877.INC . Only the critical settings are listed in the file. Any bits not listed are left in their default states, which can be found in the Special Features section of the Microchip datasheet for the PICmicro. Here we find that the PM configuration directive reads:
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To find the correct labels that set the configuration bits as we need them, view the PM header file at C:\PBP\INC\M16F87x.INC. Here we find the labels we need:
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; *** DEVICE Fuses Definitions RC_OSC equ 3FFC0003h ; XX XXXX XXXX XX11 HS_OSC equ 3FFC0002h ; XX XXXX XXXX XX10 XT_OSC equ 3FFC0001h ; XX XXXX XXXX XX01 LP_OSC equ 3FFC0000h ; XX XXXX XXXX XX00 WDT_ON equ 3FFB0004h ; XX XXXX XXXX X1XX WDT_OFF equ 3FFB0000h ; XX XXXX XXXX X0XX PWRT_ON equ 3FF70000h ; XX XXXX XXXX 0XXX PWRT_OFF equ 3FF70008h ; XX XXXX XXXX 1XXX BOD_ON equ 3FBF0040h ; XX XXXX X1XX XXXX BOD_OFF equ 3FBF0000h ; XX XXXX X0XX XXXX LVP_ON equ 3F7F0080h ; XX XXXX 1XXX XXXX LVP_OFF equ 3F7F0000h ; XX XXXX 0XXX XXXX CPD_ON equ 3EFF0000h ; XX XXX0 XXXX XXXX CPD_OFF equ 3EFF0100h ; XX XXX1 XXXX XXXX WRT_ON equ 3DFF0200h ; XX XX1X XXXX XXXX WRT_OFF equ 3DFF0000h ; XX XX0X XXXX XXXX DEBUG_ON equ 37FF0000h ; XX 0XXX XXXX XXXX DEBUG_OFF equ 37FF0800h ; XX 1XXX XXXX XXXX PROTECT_ON equ 0FCF0000h ; 00 XXXX XX00 XXXX PROTECT_OFF equ 0FCF3030h ; 11 XXXX XX11 XXXX |
Replacing the appropriate labels and putting the "@" at the beginning of the line to signify inline assembly, the configuration line in our PICBASIC PRO source file becomes:
| @ device pic16F877, hs_osc, wdt_on, pwrt_on, lvp_off, protect_on |
Some of the newer PIC16 MCUs have multiple configuration words. An example is the PIC16F88. When you open the .INC file for these devices, you will see a section of labels denoted with the "DEVICE2" heading:
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; *** DEVICE2 Fuses Definitions FCMEN_OFF equ 3FFE0000h ; XX XXXX XXXX XXX0 FCMEN_ON equ 3FFE0001h ; XX XXXX XXXX XXX1 IESO_OFF equ 3FFD0000h ; XX XXXX XXXX XX0X IESO_ON equ 3FFD0002h ; XX XXXX XXXX XX1X |
When using configuration labels from this section, a special directive "device2" must be used, as follows:
| @ device2 pic16F88, fcmen_off, ieso_off |
PM will always take the configuration that is placed in the program source code. There is no need to comment or remove the line in the .INC file.
Procedure for MPASMWIN.EXE:
A note about deprecation of the __CONFIG directive
Let's look at an example using the 18F452 and setting the oscillator configuration to HS. Assuming the compiler is installed at C:\PBP, we view the file C:\PBP\18F452.INC . Only the critical settings are listed in the file. Any bits not listed are left in their default states, which can be found in the Special Features section of the Microchip datasheet for the PICmicro. Here we find that the MPASM configuration directive reads:
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INCLUDE "P18F452.INC" ; MPASM Header
__CONFIG _CONFIG1H, _OSCS_OFF_1H & _XT_OSC_1H
__CONFIG _CONFIG2H, _WDT_ON_2H & _WDTPS_128_2H
__CONFIG _CONFIG4L, _LVP_OFF_4L
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To find the correct labels that set the configuration bits as we need them, view the MPASM header file found in C:\Program Files\MPLAB IDE\MCHIP_Tools\P18F452.INC. Here we find the label we need:
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;Configuration Byte 1H Options _OSCS_ON_1H EQU H'DF' ; Oscillator Switch enable _OSCS_OFF_1H EQU H'FF' _LP_OSC_1H EQU H'F8' ; Oscillator type _XT_OSC_1H EQU H'F9' _HS_OSC_1H EQU H'FA' _RC_OSC_1H EQU H'FB' _EC_OSC_1H EQU H'FC' ; External Clock w/OSC2 output divide by 4 _ECIO_OSC_1H EQU H'FD' ; w/OSC2 as an IO pin (RA6) _HSPLL_OSC_1H EQU H'FE' ; HS PLL _RCIO_OSC_1H EQU H'FF' ; RC w/OSC2 as an IO pin (RA6) |
Replacing the appropriate labels and putting the "@" at the beginning of the line to signify inline assembly, the configuration line in our PICBASIC PRO source file becomes:
@ __CONFIG _CONFIG1H, _OSCS_OFF_1H & _HS_OSC_1H |
To avoid an error caused by multiple configuration lines, the original line must be commented in the file 18F452.INC. A semicolon (;) is used for comments in Assembly language:
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INCLUDE "P18F452.INC" ; MPASM Header
; __CONFIG _CONFIG1H, _OSCS_OFF_1H & _XT_OSC_1H
__CONFIG _CONFIG2H, _WDT_ON_2H & _WDTPS_128_2H
__CONFIG _CONFIG4L, _LVP_OFF_4L
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