80CL31 Datasheet, PDF (10/40 Pages) NXP Semiconductors – Low-voltage single-chip 8-bit microcontrollers

Philips Semiconductors
Low-voltage single-chip 8-bit microcontrollers
Product specification
80CL31/80CL51
Timer 0 and Timer 1 can be independently programmed to operate
as follows:
Mode 0 - 8-bit timer or counter with divide-by-32 prescaler
Mode 1 - 16-bit time-interval or event counter
Mode 2 - 8-bit time interval or event counter with automatic reload
upon overflow
Mode 3 - Timer 0 establishes TL0 and TH0 as two separate
counters.
In the “Timer” function, the register is incremented every machine
cycle. Since a machine cycle consists of 12 oscillator periods, the
count rate is 1/12 of the oscillator frequency.
In the “Counter” function, the register is incremented in response to
a 1-to-0 transition. Since it takes 2 machine cycles (24 oscillator
periods) to recognize a 1-to-0 transition, the maximum count rate is
1/24 of the oscillator frequency. To ensure a given level is sampled,
it should be held for at least one full machine cycle.
1.4 Idle and Power-down operation
Idle mode operation permits the interrupt, serial port and timer
blocks to continue functioning while the clock to the CPU is halted.
The following functions remain active during Idle mode:
– Timer 0, Timer 1
– UART
– External interrupt
The Power-down operation freezes the oscillator. The Power-down
mode can only be activated by setting the PD bit in the PCON
register.
1.4.1 Power control register
Power-down and Idle modes are activated by software via the
Special Function Register PCON. Its hardware address is 87H.
PCON is byte addressable only.
BIT
SMOD
GF1
GFO
PD
IDL
POSITION
PCON.7
PCON.4-PCON.6
PCON.3
PCON.2
PCON.1
PCON.0
PCON
FUNCTION
Double baud-rate bit, see description of the UART, chapter 1.5.
(reserved)
General purpose flag bit
General purpose flag bit
Power-down activation bit
Idle mode activation bit
XTAL2
XTAL1
OSCILLATOR
PD
CLOCK
GENERATOR
January 1995
Figure 4. Idle and Power-down Hardware
10
INPUTS
SERIAL PORTS
TIMER BLOCKS
CPU
IDL