PIC24F04KA200 Datasheet, PDF (18/26 Pages) Microchip Technology – Flash Programming Specifications

PIC24FXXKA2XX
3.8 Reading Code Memory
To read the code memory, execute a series of TBLRD
instructions and clock out the data using the REGOUT
command.
Table 3-9 provides the ICSP programming details for
reading code memory. In Step 1, the Reset vector is
exited. In Step 2, the 24-bit starting source address for
reading is loaded into the TBLPAG register and the W6
register. The upper byte of the starting source address
is stored in TBLPAG, and the lower 16 bits of the source
address are stored in W6.
To minimize the reading time, the packed instruction
word format, which was used for writing, is also used
for reading (see Figure 3-7). In Step 3, the Write
Pointer, W7, is initialized. In Step 4, two instruction
words are read from code memory, and clocked out of
the device through the VISI register, using the REGOUT
command. Step 4 is repeated until the required amount
of code memory is read.
TABLE 3-9: SERIAL INSTRUCTION EXECUTION FOR READING CODE MEMORY
Command
(Binary)
Data
(Hex)
Description
Step 1: Exit Reset vector.
0000
0000
0000
000000
040200
000000
NOP
GOTO
NOP
0x200
Step 2: Initialize TBLPAG and the Read Pointer (W6) for TBLRD instruction.
0000
0000
0000
200xx0 MOV
880190 MOV
2xxxx6 MOV
#<SourceAddress23:16>, W0
W0, TBLPAG
#<SourceAddress15:0>, W6
Step 3: Initialize the Write Pointer (W7) to point to the VISI register.
0000
0000
207847 MOV
000000 NOP
#VISI, W7
Step 4: Read and clock out the contents of the next two locations of code memory through the VISI register using
the REGOUT command.
0000
0000
0000
0001
0000
0000
0000
0000
0000
0000
0000
0001
0000
0000
0000
0000
0001
0000
BA1B96
000000
000000
<VISI>
000000
BADBB6
000000
000000
BAD3D6
000000
000000
<VISI>
000000
BA0BB6
000000
000000
<VISI>
000000
TBLRDL [W6], [W7]
NOP
NOP
Clock out contents of VISI register.
NOP
TBLRDH [W6++], [W7]
NOP
NOP
TBLRDH.B [++W6], [W7--]
NOP
NOP
Clock out contents of VISI register.
NOP
TBLRDL [W6++], [W7]
NOP
NOP
Clock out contents of VISI register.
NOP
Step 5: Reset device internal PC.
0000
0000
040200 GOTO
000000 NOP
0x200
Step 6: Repeat Steps 4 and 5 until the required code memory is read.
DS39991A-page 18
 2010 Microchip Technology Inc.