Microchip Technology IC PIC MCU PIC16F1937-I/PT TQFP-44 MCP PIC16F1937-I/PT Data Sheet
Product codes
PIC16F1937-I/PT
2008-2011 Microchip Technology Inc.
DS41364E-page 27
PIC16(L)F1934/6/7
3.1.1
READING PROGRAM MEMORY AS
DATA
DATA
There are two methods of accessing constants in pro-
gram memory. The first method is to use tables of
RETLW
gram memory. The first method is to use tables of
RETLW
instructions. The second method is to set an
FSR to point to the program memory.
3.1.1.1
RETLW
Instruction
The RETLW instruction can be used to provide access
to tables of constants. The recommended way to create
such a table is shown in
to tables of constants. The recommended way to create
such a table is shown in
EXAMPLE 3-1:
RETLW
INSTRUCTION
The BRW instruction makes this type of table very sim-
ple to implement. If your code must remain portable
with previous generations of microcontrollers, then the
BRW
ple to implement. If your code must remain portable
with previous generations of microcontrollers, then the
BRW
instruction is not available so the older table read
method must be used.
constants
BRW
;Add Index in W to
;program counter to
;select data
RETLW DATA0
;Index0 data
RETLW DATA1
;Index1 data
RETLW DATA2
RETLW DATA3
my_function
;… LOTS OF CODE…
MOVLW
DATA_INDEX
call constants
;… THE CONSTANT IS IN W