PIC17C756A MICROCHIP [Microchip Technology], PIC17C756A Datasheet - Page 59

• Manufacturer Part Number: PIC17C756A
• Description: High-Performance 8-bit CMOS EPROM Microcontrollers with 10-bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

8.0
The PIC17C7XX has four instructions that allow the
processor to move data from the data memory space to
the program memory space, and vice versa. Since the
program memory space is 16-bits wide and the data
memory space is 8-bits wide, two operations are
required to move 16-bit values to/from the data
memory.
The TLWT t,f and TABLWT t,i,f instructions are
used to write data from the data memory space to the
program memory space. The TLRD t,f and TABLRD
t,i,f instructions are used to write data from the pro-
gram memory space to the data memory space.
The program memory can be internal or external. For
the program memory access to be external, the device
needs to be operating in Microprocessor or Extended
Microcontroller mode.
Figure 8-1 through Figure 8-4 show the operation of
these four instructions. The steps show the sequence
of operation.
FIGURE 8-1:
Step 1: 8-bit value from register ’f’, loaded into the high or low
2000 Microchip Technology Inc.
Memory
Data
f
TABLE READS AND TABLE
WRITES
byte in TABLAT (16-bit).
TABLE POINTER
TABLE LATCH (16-bit)
TLWT 1,f
1
TBLPTRH
TABLATH
TLWT INSTRUCTION
OPERATION
TBLPTRL
TABLATL
TLWT 0,f
Program Memory
FIGURE 8-2:
Step 1: 8-bit value from register ’f’, loaded into the high or low
Memory
Data
2: 16-bit TABLAT value written to address Program Memory
3: If “i” = 1, then TBLPTR = TBLPTR + 1,
f
TABLWT 1,i,f
byte in TABLAT (16-bit).
(TBLPTR).
If “i” = 0, then TBLPTR is unchanged.
TABLE POINTER
TABLE LATCH (16-bit)
1
3
TBLPTRH
TABLATH
TABLWT INSTRUCTION
OPERATION
Prog-Mem
(TBLPTR)
PIC17C7XX
2
TBLPTRL
TABLATL
TABLWT 0,i,f
Program Memory
DS30289B-page 59
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