PIC16F193X Datasheet, PDF (330/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

PIC16F193X/LF193X
23.2 Erasing Program Memory
While executing code, program memory can only be
erased by rows. A row consists of 32 words where the
EEADRL<4:0> = 0000. To erase a row:
1. Load the EEADRH and EEADRL registers with
the address of new row to be erased.
2. Clear the CFGS bit of the EECON1 register.
3. Set the EEPGD bit of the EECON1 register.
4. Set the FREE bit of the EECON1 register.
5. Write 55h, then AAh, to EECON2 (Flash
programming unlock sequence).
6. Set control bit WR of the EECON1 register to
begin the write operation.
23.3 Writing to Flash Program Memory
Before writing, program memory should be erased
using the Erase Program Memory command.
No automatic erase occurs upon the initiation of the
write; if the program Flash needs to be erased before
writing, the row (32 words) must be erased previously.
Flash program memory may only be written to if the
destination address is in a segment of memory that is
not write-protected, as defined in bits WRT<1:0> of the
Configuration Word Register 2. Flash program memory
must be written in eight-word blocks. See Figure 23-2
for more details. A block consists of eight words with
sequential addresses, with a lower boundary defined
by an address, where EEADRL<2:0> = 000. All block
writes to program memory are done as 32-word erase
by eight-word write operations. The write operation is
edge-aligned and cannot occur across boundaries.
When the LWLO bit is ‘1’, the write sequence will only
load the buffer register and will not actually initiate the
write to program Flash:
1. Set the EEPGD, WREN and LWLO bits of the
EECON1 register.
2. Write 55h, then AAh, to EECON2 (Flash
programming unlock sequence).
3. Set control bit WR of the EECON1 register to
begin the write operation.
To write program data, it must first be loaded into the
buffer registers (see Figure 23-1). This is accomplished
by first writing the destination address to EEADRL and
EEADRH and then writing the data to EEDATA and
EEDATH. After the address and data have been set up,
then the following sequence of events must be executed:
1. Set the EEPGD control bit of the EECON1
register.
2. Set the LWLO bit of the EECON1 register.
3. Write 55h, then AAh, to EECON2 (Flash
programming sequence).
4. Set the WR control bit of the EECON1 register.
Up to eight buffer register locations can be written to
with correct data. If less than eight words are being writ-
ten to in the block of eight words, then the data for the
unprogrammed words should be set to all ones.
After the “BSF EECON1,WR” instruction, the processor
requires two cycles to set up the erase/write operation.
The user must place two NOP instructions after the WR
bit is set. Since data is being written to buffer registers,
the writing of the first seven words of the block appears
to occur immediately. The processor will halt internal
operations for the typical 2 ms, only during the cycle in
which the erase takes place (i.e., the last word of the
sixteen-word block erase). This is not Sleep mode as
the clocks and peripherals will continue to run. After the
eight-word write cycle, the processor will resume oper-
ation with the third instruction after the EECON1 write
instruction.
An example of the complete eight-word write sequence
is shown in Example 23-5. The initial address is loaded
into the EEADRH and EEADRL register pair; the eight
words of data are loaded using indirect addressing.
DS41364A-page 328
Preliminary
© 2008 Microchip Technology Inc.