
Philips Semiconductors
Product data
P87LPC767
Low power, low price, low pin count (20 pin)
microcontroller with 4-kbyte OTP and 8-bit A/D converter
2002 Mar 25
30
Low Voltage EPROM Operation
The EPROM array contains some analog circuits that are not
required when VDD is less than 4 V, but are required for a VDD
greater than 4 V. The LPEP bit (AUXR.4), when set by software, will
power down these analog circuits resulting in a reduced supply
current. LPEP is cleared only by power-on reset, so it may be set
ONLY for applications that always operate with VDD less than 4 V.
Reset
The P87LPC767 has an integrated power-on reset circuit which
always provides a reset when power is initially applied to the device.
It is recommended to use the internal reset whenever possible to
save external components and to be able to use pin P1.5 as a
general-purpose input pin.
The P87LPC767 can additionally be configured to use P1.5 as an
external active-low reset pin RST by programming the RPD bit in the
User Configuration Register UCFG1 to 0. The internal reset is still
active on power-up of the device. While the signal on the RST pin is
low, the P87LPC767 is held in reset until the signal goes high.
The watchdog timer on the P87LPC767 can act as an oscillator fail
detect because it uses an independent, fully on-chip oscillator.
UCFG1 is described in the System Configuration Bytes section of
this datasheet.
SU01359
87LPC767
P1.5
Pin is used as
digital input pin
Internal power-on
Reset active
UCFG1.RPD = 1 (default)
RST
Pin is used as
active-low reset pin
Internal power-on
Reset active
UCFG1.RPD = 0
Figure 22. Using pin P1.5 as general purpose input pin or as low-active reset pin
SU01170
CHIP RESET
CPU
CLOCK
Q
RESET
TIMING
RPD (UCFG1.6)
WDT
MODULE
SOFTWARE RESET
SRST (AUXR1.3)
POWER MONITOR
RESET
RST/VPP PIN
WDTE (UCFG1.7)
S
R
Figure 23. Block Diagram Showing Reset Sources