MCP19124 datasheet(134/236 Pages) MICROCHIP

134 / 236 page

MCP19124/5

DS20005619A-page 134

 2016 Microchip Technology Inc.

20.3.1

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 (bit 0

in the PMCON1 register). Once the read control bit is

set, the Program Memory Flash controller will use the

second instruction cycle to read the data. This causes

the second instruction immediately following the

BSF PMCON1,RD

instruction to be ignored. The data

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

registers will hold this value until another read or until it

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

EXAMPLE 20-1:

FLASH PROGRAM READ

FIGURE 20-1:

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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