PIC17C4X
FIGURE 7-2: TABLWT INSTRUCTION
OPERATION
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.
TABLE POINTER
TBLPTRH
TBLPTRL
TABLATL
TABLE LATCH (16-bit)
TABLATH
The TLWT t,fand TABLWT t,i,finstructions are
used to write data from the data memory space to the
program memory space. The TLRD t,fand TABLRD
t,i,finstructions are used to write data from the pro-
gram memory space to the data memory space.
3
3
TABLWT 1,i,f
TABLWT 0,i,f
DATA
MEMORY
PROGRAM MEMORY
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.
f
Figure 7-1 through Figure 7-4 show the operation of
these four instructions.
1
Prog-Mem
FIGURE 7-1: TLWT INSTRUCTION
OPERATION
(TBLPTR)
2
TABLE POINTER
TBLPTRH
TBLPTRL
TABLATL
TABLE LATCH (16-bit)
TABLATH
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).
TLWT 1,f
TLWT 0,f
PROGRAM MEMORY
DATA
MEMORY
3: If “i” = 1, then TBLPTR = TBLPTR + 1,
If “i” = 0, then TBLPTR is unchanged.
f
1
Note 1: 8-bit value, from register 'f', loaded into the
high or low byte in TABLAT (16-bit).
1996 Microchip Technology Inc.
DS30412C-page 43
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