PIC17C42A MICROCHIP [Microchip Technology], PIC17C42A Datasheet - Page 7

• Manufacturer Part Number: PIC17C42A
• Description: EPROM Memory Programming Specification
• Manufacturer: MICROCHIP [Microchip Technology]

4.0
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 in
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
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>
TABLE 4-2:
EPROM Memory Programming Specification
1996 Microchip Technology Inc.
*
—=Unused
PM<2:0>, Processor Mode Select bits
WDTPS<1:0>, WDT Prescaler Select bits.
FOSC<1:0>, Oscillator Select bits
111 = Microprocessor mode
110 = Microcontroller mode
101 = Extended Microcontroller mode
000 = Code protected microcontroller mode
11 = WDT enabled, postscaler = 0
10 = WDT enabled, postscaler = 256
01 = WDT enabled, postscaler = 64
00 = WDT disabled, 16-bit overflow timer
11 = EC oscillator
10 = XT oscillator
01 = RC oscillator
00 = LF oscillator
This bit does not exist on PIC17C42.
Reading Configuration Word
15
CONFIGURATION WORD
15
1
1
14
14
1
1
READ MAPPING OF CONFIGURATION BITS
13
13
1
1
12
12
1
1
11
11
1
1
10
10
1
1
9
1
9
1
8
1
8
1
PM2*
—
7
7
PM1
—
6
6
(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:
†
This location does not exist on the PIC17C42.
—
—
5
5
WDTPS0
WDTPS1
PM0
FOSC0
FOSC1
—
4
PM2
4
PM0
PM1
Bit
WDTPS1
†
—
CONFIGURATION BIT
PROGRAMMING LOCATIONS
3
3
WDTPS0
—
2
2
FOSC1 FOSC0
1
Address
—
1
0xFE00
0xFE01
0xFE02
0xFE03
0xFE04
0xFE06
0xFE0F
DS30139I-page 7
0
—
0