PIC16F193X Datasheet, PDF (334/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

PIC16F193X/LF193X
23.5 Write Verify
Depending on the application, good programming
practice may dictate that the value written to the data
EEPROM or program memory should be verified (see
Example 23-6) to the desired value to be written.
EXAMPLE 23-6: WRITE VERIFY
BANKSEL EEDATL
;
MOVF EEDATL, W ;EEDATL not changed
;from previous write
BSF
EECON1, RD ;YES, Read the
;value written
XORWF EEDATL, W ;
BTFSS STATUS, Z ;Is data the same
GOTO WRITE_ERR ;No, handle error
:
;Yes, continue
23.5.1 USING THE DATA EEPROM
The data EEPROM is a high-endurance, byte
addressable array that has been optimized for the
storage of frequently changing information (e.g.,
program variables or other data that are updated often).
When variables in one section change frequently, while
variables in another section do not change, it is possible
to exceed the total number of write cycles to the
EEPROM (specification D124) without exceeding the
total number of write cycles to a single byte
(specifications D120 and D120A). If this is the case,
then a refresh of the array must be performed. For this
reason, variables that change infrequently (such as
constants, IDs, calibration, etc.) should be stored in
Flash program memory.
23.6 Protection Against Spurious Write
There are conditions when the user may not want to
write to the data EEPROM memory. To protect against
spurious EEPROM writes, various mechanisms have
been built-in. On power-up, WREN is cleared. Also, the
Power-up Timer (64 ms duration) prevents
EEPROM write.
The write initiate sequence and the WREN bit together
help prevent an accidental write during:
• Brown-out
• Power Glitch
• Software Malfunction
23.7 Data EEPROM Operation During
Code-Protect
Data memory can be code-protected by programming
the CPD bit in the Configuration Word Register 1
(Register 10-1) to ‘0’.
When the data memory is code-protected, only the
CPU is able to read and write data to the data
EEPROM. It is recommended to code-protect the
program memory when code-protecting data memory.
This prevents anyone from replacing your program with
a program that will access the contents of the data
EEPROM.
TABLE 23-2: SUMMARY OF REGISTERS ASSOCIATED WITH DATA EEPROM
Name Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Register
on Page
EECON1 EEPGD CFGS LWLO FREE WRERR WREN
WR
RD
323
EECON2 EEPROM Control Register 2 (not a physical register)
EEADRL EEADRL7 EEADRL6 EEADRL5 EEADRL4 EEADRL3 EEADRL2 EEADRL1 EEADRL0
324*
322
EEADRH
— EEADRH6 EEADRH5 EEADRH4 EEADRH3 EEADRH2 EEADRH1 EEADRH0 322
EEDATL EEDATL7 EEDATL6 EEDATL5 EEDATL4 EEDATL3 EEDATL2 EEDALT1 EEDATL0 322
EEDATH
—
INTCON GIE
— EEDATH5 EEDATH4 EEDATH3 EEDATH2 EEDATH1 EEDATH0 322
PEIE TMR0IE INTE
IOCIE TMR0IF INTF
IOCIF
73
PIE2
OSFIE C2IE
C1IE
EEIE
BCLIE LCDIE
—
CCP2IE
75
PIR2
OSFIF C2IF
C1IF
EEIF
BCLIF LCDIF
—
CCP2IF
78
Legend: x = unknown, u = unchanged, — = unimplemented read as ‘0’, q = value depends upon condition.
Shaded cells are not used by data EEPROM module.
* Page provides register information.
DS41364A-page 332
Preliminary
© 2008 Microchip Technology Inc.