PIC17C43 datasheet(7/16 Pages) MICROCHIP

7 / 16 page

DS30139I-page 7

EPROM Memory Programming Specification

4.0

CONFIGURATION WORD

Conﬁguration bits are mapped into program memory.

Each bit is assigned one memory location. In erased

condition a bit will read as '1'. To program a bit, the user

needs to write to the memory address. The data is

immaterial; the very act of writing will program the bit.

The

conﬁguration

word

locations

are

shown

Table 4-3. The programmer should not program the

reserved locations to avoid unpredictable results

and to be compatible with future variations of the

PIC17C4X. It is also mandatory that conﬁguration

locations are programmed in the strict order start-

ing from the ﬁrst location (0xFE00) and ending with

the last (0xFE0F). Unpredictable results may occur

if the sequence is violated.

4.1

Reading Conﬁguration Word

The PIC17CXX has seven conﬁguration locations (see

Table 4-1). These locations can be programmed (read

as '0') or left unprogrammed (read as '1') to select var-

ious device conﬁgurations. Any write to a conﬁguration

location, regardless of the data, will program that con-

ﬁguration bit. Reading any conﬁguration location

between 0xFE00 and 0xFE07 will place the low byte of

the conﬁguration word (see Table 4-2) into PAD<7:0>

(PORTC). PAD<15:8> (PORTB) will be set to 0xFF.

Reading a conﬁguration location between 0xFE08 and

0xFE0F will place the high byte of the conﬁguration

word into PAD<7:0> (PORTC). PAD<15:8> (PORTB)

will be set to 0xFF.

TABLE 4-1:

CONFIGURATION BIT

PROGRAMMING LOCATIONS

†This location does not exist on the PIC17C42.

Bit

Address

FOSC0

0xFE00

FOSC1

0xFE01

WDTPS0

0xFE02

WDTPS1

0xFE03

PM0

0xFE04

PM1

0xFE06

PM2†

0xFE0F

TABLE 4-2:

READ MAPPING OF CONFIGURATION BITS

—=Unused

PM<2:0>, Processor Mode Select bits

111 = Microprocessor mode

110 = Microcontroller mode

101 = Extended Microcontroller mode

000 = Code protected microcontroller mode

WDTPS<1:0>, WDT Prescaler Select bits.

= WDT enabled, postscaler = 0

= WDT enabled, postscaler = 256

= WDT enabled, postscaler = 64

= WDT disabled, 16-bit overﬂow timer

FOSC<1:0>, Oscillator Select bits

= EC oscillator

= XT oscillator

= RC oscillator

= LF oscillator

* This bit does not exist on PIC17C42.

WDTPS1

FOSC1 FOSC0

WDTPS0

PM0

PM1

—

PM2*

——

—

——

—

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