Table of Contents
Advertisement
Philips Semiconductors
FLASH MEMORY
User configuration bytes
A number of user-configurable features of the P89LPC920/921/922 must be defined at power-up and therefore cannot be set by
the program after start of execution. These features are configured through the use of an Flash byte UCFG1 shown in Figure 15-
5.
UCFG1
Address: xxxxh
Unprogrammed value: 63h
BIT
SYMBOL
UCFG1.7
WDTE
UCFG1.6
RPE
UCFG1.5
BOE
UCFG1.4
WDSE
UCFG1.3
-
UCFG1.2-0
FOSC2-FSOC0
FOSC2-FOSC0
1 1 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Factory default value for UCFG1 is set for watchdog reset disabled, reset pin enabled, brownout detect enabled, and using
the internal RC oscillator
2003 Dec 8
7
6
WDTE
RPE
FUNCTION
Watchdog timer reset enable. When set =1, enables the watchdog timer reset. When
cleared = 0, disables the watchdog timer reset. The timer may still be used to generate an
interrupt. Refer to Table 13-1 for details.
Reset pin enable. When set =1, enables the reset function of pin P1.5. When cleared, P1.5
may be used as an input pin. NOTE: During a power-up sequence, the RPE selection is
overriden and this pin will always functions as a reset input. After power-up the pin will
function as defined by the RPE bit. Only a power-up reset will temporarily override the
selection defined by RPE bit. Other sources of reset will not override the RPE bit.
Brownout Detect Enable (see section "Brownout Detection" on page 33).
Watchdog Safety Enable bit. Refer to Table 13-1 for details.
Reserved (should remain unprogrammed at zero).
CPU oscillator type select. See section "Clocks" on page 21 for additional information.
Combinations other than those shown below should not be used. They are reserved for
future use.
Oscillator Configuration
External clock input on XTAL1.
Watchdog Oscillator, 400 kHz (+20/ -30% tolerance).
Internal RC oscillator, 7.373 MHz ±2.5%.
Low frequency crystal, 20 kHz to 100 kHz.
Medium frequency crystal or resonator, 100 kHz to 4 MHz.
High frequency crystal or resonator, 4 MHz to 12 MHz.
Figure 15-5: Flash User Configuration Byte 1 (UCFG1)
5
4
3
BOE
WDSE
-
109
User's Manual - Preliminary -
P89LPC920/921/922
2
1
0
FOSC2
FOSC1
FOSC0
Advertisement
Table of Contents
