PIC18F2423-I/ML Microchip Technology, PIC18F2423-I/ML Datasheet - Page 15

• Manufacturer Part Number: PIC18F2423-I/ML
• Description: 16KB, Flash, 768bytes-RAM, 25I/O, 8-bit Family,nanoWatt 28 QFN 6x6mm TUBE
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F2423-I/ML

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, HLVD, POR, PWM, WDT
• Number Of I /o: 25
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 10x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: XLT28QFN4 - SOCKET TRANS ICE 28QFN W/CABLEAC164322 - MODULE SOCKET MPLAB PM3 28/44QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

3.2.1
The previous programming example assumed that the
device had been Bulk Erased prior to programming
(see Section 3.1.1 “High-Voltage ICSP Bulk Erase”).
It may be the case, however, that the user wishes to
modify only a section of an already programmed
device.
TABLE 3-6:
© 2005 Microchip Technology Inc.
Step 1: Direct access to code memory.
Step 2: Read and modify code memory (see Section 4.1 “Read Code Memory, ID Locations and Configuration Bits”).
Step 3: Set the Table Pointer for the block to be erased.
Step 4: Enable memory writes and setup an erase.
Step 5: Initiate erase.
Step 6: Load write buffer. The correct bytes will be selected based on the Table Pointer.
To continue modifying data, repeat Steps 2 through 6, where the Address Pointer is incremented by the appropriate number of bytes
(see Table 3-4) at each iteration of the loop. The write cycle must be repeated enough times to completely rewrite the contents of
the erase buffer.
Step 7: Disable writes.
Command
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
1101
1111
0000
0000
4-Bit
.
.
.
MODIFYING CODE MEMORY
8E A6
9C A6
0E <Addr[21:16]>
6E F8
0E <Addr[8:15]>
6E F7
0E <Addr[7:0]>
6E F6
84 A6
88 A6
82 A6
00 00
0E <Addr[21:16]>
6E F8
0E <Addr[8:15]>
6E F7
0E <Addr[7:0]>
6E F6
<MSB><LSB>
<MSB><LSB>
00 00
94 A6
MODIFYING CODE MEMORY
Data Payload
.
.
.
BSF
BCF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
BSF
BSF
NOP - hold PGC high for time P9 and low for time P10.
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
Write 2 bytes and post-increment address by 2.
Repeat as many times as necessary to fill the write buffer
Write 2 bytes and start programming.
NOP - hold PGC high for time P9 and low for time P10.
BCF
PIC18F2423/2523/4423/4523
EECON1, EEPGD
EECON1, CFGS
<Addr[21:16]>
TBLPTRU
<Addr[8:15]>
TBLPTRH
<Addr[7:0]>
TBLPTRL
EECON1, WREN
EECON1, FREE
EECON1, WR
<Addr[21:16]>
TBLPTRU
<Addr[8:15]>
TBLPTRH
<Addr[7:0]>
TBLPTRL
EECON1, WREN
The appropriate number of bytes required for the erase
buffer must be read out of code memory (as described
in Section 4.2 “Verify Code Memory and ID
Locations”) and buffered. Modifications can be made
on this buffer. Then, the block of code memory that was
read out must be erased and rewritten with the
modified data.
The WREN bit must be set if the WR bit in EECON1 is
used to initiate a write sequence.
Core Instruction
DS39759A-page 15