OPTION_REG datasheet(106/222 Pages) MICROCHIP

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MCP19111

DS22331A-page 106

 2013 Microchip Technology Inc.

18.3.1

READING THE FLASH PROGRAM

MEMORY

To read a program memory location, the user must

write two bytes of the address to the PMADRL and

PMADRH registers, and then set control bit RD

(PMCON1<0>). Once the read control bit is set, the

program memory Flash controller will use the second

instruction cycle after to read the data. This causes the

second instruction immediately following the “BSF

PMCON1,RD

” instruction to be ignored. The data is

available, in the very next cycle, in the PMDATL and

PMDATH registers; it can be read as two bytes in the

following instructions. PMDATL and PMDATH regis-

ters will hold this value until another read or until it is

written to by the user (during a write operation).

EXAMPLE 18-1:

FLASH PROGRAM READ

FIGURE 18-1:

FLASH PROGRAM MEMORY READ CYCLE EXECUTION – NORMAL MODE

BANKSELPM_ADR; Change STATUS bits RP1:0 to select bank with PMADR

MOVLWMS_PROG_PM_ADDR;

MOVWFPMADRH; MS Byte of Program Address to read

MOVLWLS_PROG_PM_ADDR;

MOVWFPMADRL; LS Byte of Program Address to read

BANKSELPMCON1; Bank to containing PMCON1

BSF PMCON1, RD; EE Read

NOP

; First instruction after BSF PMCON1,RD executes normally

NOP

; Any instructions here are ignored as program

; memory is read in second cycle after BSF PMCON1,RD

;

BANKSELPMDATL; Bank to containing PMADRL

MOVFPMDATL, W; W = LS Byte of Program PMDATL

MOVFPMDATH, W; W = MS Byte of Program PMDATL

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

BSF PMCON1,RD

Executed here

INSTR (PC + 1)

Executed here

NOP

Executed here

PC + 1

PMADRH,PMADRL

PC+3

PC + 5

Flash ADDR

RD bit

INSTR (PC)

PMDATH,PMDATL

INSTR (PC + 3)

PC + 3

PC + 4

INSTR (PC + 4)

INSTR (PC + 1)

INSTR (PC - 1)

Executed here

INSTR (PC + 3)

Executed here

INSTR (PC + 4)

Executed here

Flash DATA

PMDATH

PMDATL

EERHLT

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