Microchip Technology MA160014 Data Sheet
PIC18(L)F2X/4XK22
DS41412F-page 96
2010-2012 Microchip Technology Inc.
FIGURE 6-2:
TABLE WRITE OPERATION
6.2
Control Registers
Several control registers are used in conjunction with
the TBLRD and TBLWT instructions. These include the:
the TBLRD and TBLWT instructions. These include the:
• EECON1 register
• EECON2 register
• TABLAT register
• TBLPTR registers
6.2.1
EECON1 AND EECON2 REGISTERS
The EECON1 register (
) is the control
register for memory accesses. The EECON2 register is
not a physical register; it is used exclusively in the
memory write and erase sequences. Reading
EECON2 will read all ‘0’s.
not a physical register; it is used exclusively in the
memory write and erase sequences. Reading
EECON2 will read all ‘0’s.
The EEPGD control bit determines if the access will be
a program or data EEPROM memory access. When
EEPGD is clear, any subsequent operations will
operate on the data EEPROM memory. When EEPGD
is set, any subsequent operations will operate on the
program memory.
a program or data EEPROM memory access. When
EEPGD is clear, any subsequent operations will
operate on the data EEPROM memory. When EEPGD
is set, any subsequent operations will operate on the
program memory.
The CFGS control bit determines if the access will be
to the Configuration/Calibration registers or to program
memory/data EEPROM memory. When CFGS is set,
subsequent operations will operate on Configuration
registers regardless of EEPGD (see
to the Configuration/Calibration registers or to program
memory/data EEPROM memory. When CFGS is set,
subsequent operations will operate on Configuration
registers regardless of EEPGD (see
). When CFGS is clear,
memory selection access is determined by EEPGD.
The FREE bit allows the program memory erase
operation. When FREE is set, an erase operation is
initiated on the next WR command. When FREE is
clear, only writes are enabled.
operation. When FREE is set, an erase operation is
initiated on the next WR command. When FREE is
clear, only writes are enabled.
The WREN bit, when set, will allow a write operation.
The WREN bit is clear on power-up.
The WREN bit is clear on power-up.
The WRERR bit is set by hardware when the WR bit is
set and cleared when the internal programming timer
expires and the write operation is complete.
set and cleared when the internal programming timer
expires and the write operation is complete.
The WR control bit initiates write operations. The WR
bit cannot be cleared, only set, by firmware. Then WR
bit is cleared by hardware at the completion of the write
operation.
bit cannot be cleared, only set, by firmware. Then WR
bit is cleared by hardware at the completion of the write
operation.
Table Pointer
(1)
Table Latch (8-bit)
TBLPTRH
TBLPTRL
TABLAT
Program Memory
(TBLPTR<MSBs>)
TBLPTRU
Instruction: TBLWT*
Note
1: During table writes the Table Pointer does not point directly to Program Memory. The LSBs of TBLPRTL
actually point to an address within the write block holding registers. The MSBs of the Table Pointer deter-
mine where the write block will eventually be written. The process for writing the holding registers to the
program memory array is discussed in
mine where the write block will eventually be written. The process for writing the holding registers to the
program memory array is discussed in
Holding Registers
Program Memory
Note:
During normal operation, the WRERR is
read as ‘1’. This can indicate that a write
operation was prematurely terminated by
a Reset, or a write operation was
attempted improperly.
read as ‘1’. This can indicate that a write
operation was prematurely terminated by
a Reset, or a write operation was
attempted improperly.
Note:
The EEIF interrupt flag bit of the PIR2
register is set when the write is complete.
The EEIF flag stays set until cleared by
firmware.
register is set when the write is complete.
The EEIF flag stays set until cleared by
firmware.