PIC16C926 Microchip Technology Inc., PIC16C926 Datasheet - Page 30

• Manufacturer Part Number: PIC16C926
• Description: 64/68-pin Cmos Microcontrollers With Lcd Driver
• Manufacturer: Microchip Technology Inc.

PIC16C925/926
3.3
A program memory location may be read by writing two
bytes of the address to the PMADR and PMADRH reg-
isters, and then setting control bit RD (PMCON1<0>).
Once the read control bit is set, the microcontroller will
use the next two instruction cycles to read the data. The
EXAMPLE 3-1:
3.4
If the program memory is not code protected, the pro-
gram memory control can read anywhere within the
program memory.
If the entire program memory is code protected, the
program memory control can read anywhere within the
program memory.
TABLE 3-1:
DS39544A-page 28
10Ch
18Ch
18Dh
18Eh
18Fh
Legend: x = unknown, u = unchanged, r = reserved, - = unimplemented, read as '0'.
Note 1: This bit always reads as a ‘1’.
;
;
;
Address
BSF
BSF
MOVLW
MOVWF
MOVLW
MOVWF
BCF
BSF
BSF
NOP
MOVF
MOVF
Reading the Program Memory
Operation During Code Protect
Shaded cells are not used during FLASH access.
PMCON1
PMDATA
PMADR
PMDATH
PMADRH
Name
STATUS, RP1
STATUS, RP0
MS_PROG_PM_ADDR
PMADRH
LS_PROG_PM_ADDR
PMADR
STATUS, RP0
PMCON1, RD
STATUS, RP0
PMDATA, W
PMDATH, W
REGISTERS ASSOCIATED WITH PROGRAM MEMORY
Data Register Low Byte
Address Register Low Byte
PROGRAM READ
Bit 7
(1)
—
—
Bit 6
—
—
—
Data Register High Byte
Bit 5
—
—
;
; Bank 3
;
; MS Byte of Program Address to read
;
; LS Byte of Program Address to read
; Bank 2
; PM Read
; First instruction after BSF PMCON1,RD executes normally
; Bank 3
; Any instructions here are ignored as program
; memory is read in second cycle after BSF PMCON1,RD
; W = LS Byte of Program PMDATA
; W = MS Byte of Program PMDATA
Address Register High Byte
Preliminary
Bit 4
—
Bit 3
—
data is available in the PMDATA and PMDATH regis-
ters after the NOP instruction. Therefore, it can be read
as two bytes in the following instructions. The PMDATA
and PMDATH registers will hold this value until another
read operation.
If only part of the program memory is code protected,
the program memory control can read the unprotected
segment and cannot read the protected segment. The
protected area cannot be read, because it may be
possible to write a downloading routine into the
unprotected segment.
Bit 2
—
Bit 1
—
Bit 0
RD
2001 Microchip Technology Inc.
1--- ---0 1--- ---0
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
POR, BOR
Value on:
Value on
RESETS
all other