PIC16C781 datasheet(49/186 Pages) MICROCHIP

49 / 186 page

 2001 Microchip Technology Inc.

Preliminary

DS41171A-page 47

PIC16C781/782

4.0

PROGRAM MEMORY READ

(PMR)

Program memory is readable during normal operation

(full VDD range). It is read by indirect addressing

through the following Special Function Registers:

• PMCON1: Control

• PMDATH: Data High

• PMDATL: Data Low

• PMADRH: Address High

• PMADRL: Address Low

When interfacing to the program memory block, the

PMDATH and PMDATL registers form a 2-byte word,

which holds the 14-bit data. The PMADRH and

PMADRL registers form a 2-byte word, which holds the

12-bit address of the program memory location being

accessed. Mid-range devices have up to 8K words of

program EPROM with an address range from 0h to

3FFFh. When the device contains less memory than

the full address range of the PMADRH:PMARDL regis-

ters, the Most Significant bits of the PMADRH register

are ignored.

4.1

PMCON1 Register

PMCON1 is the control register for program memory

accesses.

Control bit RD initiates a read operation. This bit cannot

be cleared, only set, in software. It is cleared in hard-

ware at completion of the read operation.

4.2

PMDATH and PMDATL Registers

The PMDATH:PMDATL registers are loaded with the

contents of program memory addressed by the

PMADRH and PMADRL registers upon completion of a

Program Memory Read command.

PROGRAM MEMORY READ CONTROL REGISTER 1 (PMCON1: 18Ch)

PROGRAM MEMORY DATA HIGH (PMDATH: 10Eh)

R-1

U-0

R/S-0

Reserved

—

bit7

bit0

bit 7

Reserved: Read as ‘1’

bit 6-1

Unimplemented: Read as '0

bit 0

RD: Read Control bit

= Initiates a Program memory read (read takes 2 cycles, RD is cleared in hardware)

= Reserved

Legend:

S = Settable bit

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

’1’ = Bit is set

’0’ = Bit is cleared

x = Bit is unknown

U-0

R/W-0

—

PMD13

PMD12

PMD11

PMD10

PMD9

PMD8

bit7

bit0

bit 7-6

Unimplemented: Read as '0

bit 5-0

PMD<13:8>: Program Memory Data bits

The value of the program memory word pointed to by PMADRH and PMADRL after a program

memory read command.

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

’1’ = Bit is set

’0’ = Bit is cleared

x = Bit is unknown

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