PIC17C42 Microchip Technology, PIC17C42 Datasheet - Page 43

• Manufacturer Part Number: PIC17C42
• Description: High-Performance 8-Bit CMOS EPROM/ROM Microcontroller
• Manufacturer: Microchip Technology

7.0
The PIC17C4X has four instructions that allow the pro-
cessor 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 mem-
ory.
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 extended microcontroller or
microprocessor mode.
Figure 7-1 through Figure 7-4 show the operation of
these four instructions.
FIGURE 7-1:
Note 1: 8-bit value, from register 'f', loaded into the
1996 Microchip Technology Inc.
MEMORY
DATA
f
TABLE READS AND TABLE
WRITES
high or low byte in TABLAT (16-bit).
TABLE POINTER
TABLE LATCH (16-bit)
TLWT
1
TBLPTRH
TABLATH
1,f
TLWT INSTRUCTION
OPERATION
TBLPTRL
TABLATL
This document was created with FrameMaker 4 0 4
TLWT
PROGRAM MEMORY
0,f
FIGURE 7-2:
Note 1: 8-bit value, from register 'f', loaded into
MEMORY
DATA
f
2: 16-bit TABLAT value written to address
3: If “i” = 1, then TBLPTR = TBLPTR + 1,
TABLWT
the
Program Memory (TBLPTR).
If “i” = 0, then TBLPTR is unchanged.
TABLE POINTER
TABLE LATCH (16-bit)
1
3
1,i,f
high or low byte in TABLAT (16-bit).
TBLPTRH
TABLATH
TABLWT INSTRUCTION
OPERATION
Prog-Mem
(TBLPTR)
2
PIC17C4X
TBLPTRL
TABLATL
TABLWT
PROGRAM MEMORY
DS30412C-page 43
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0,i,f