PIC17C4X Datasheet, PDF (43/240 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM/ROM Microcontroller

7.0 TABLE READS AND TABLE
WRITES
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: TLWT INSTRUCTION
OPERATION
TABLE POINTER
TBLPTRH
TBLPTRL
TABLE LATCH (16-bit)
TABLATH TABLATL
TLWT 1,f
DATA
MEMORY
TLWT 0,f
PROGRAM MEMORY
f
1
PIC17C4X
FIGURE 7-2: TABLWT INSTRUCTION
OPERATION
TABLE POINTER
TBLPTRH
TBLPTRL
TABLE LATCH (16-bit)
TABLATH TABLATL
3
TABLWT 1,i,f
DATA
MEMORY
3
TABLWT 0,i,f
PROGRAM MEMORY
f
1
Prog-Mem
(TBLPTR)
2
Note 1: 8-bit value, from register 'f', loaded into
the high or low byte in TABLAT (16-bit).
2: 16-bit TABLAT value written to address
Program Memory (TBLPTR).
3: If “i” = 1, then TBLPTR = TBLPTR + 1,
If “i” = 0, then TBLPTR is unchanged.
Note 1: 8-bit value, from register 'f', loaded into the
high or low byte in TABLAT (16-bit).
© 1996 Microchip Technology Inc.
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