87C752 Philips Semiconductors, 87C752 Datasheet - Page 8

• Manufacturer Part Number: 87C752
• Description: 80C51 8-bit microcontroller family 2K/64 OTP/ROM/ 5 channel 8 bit A/D/ I2C/ PWM/ low pin count
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Interrupt Enable Register
Position Symbol
IE.7
IE.6
IE.5
IE.4
IE.3
IE.2
IE.1
IE.0
Serial Communications
The 8XC752 contains an I
the 80C51 UART. The I
interface with all of the hardware necessary to support multimaster
and slave operations. Also included are receiver digital filters and
timer (timer I) for communication watch-dog purposes. The I
serial port is controlled through four special function registers; I
control, I
The I
between devices connected to the bus. The main technical features
of the bus are:
A large family of I
for more details on the bus and available ICs.
The 83C752 I
software required to drive the I
that on the 83C751. (See the 83C751 section for a detailed
discussion of this subsystem).
1999 Jul 23
MSB
Bidirectional data transfer between masters and slaves
Serial addressing of slaves
Acknowledgment after each transferred byte
Multimaster bus
Arbitration between simultaneously transmitting master without
corruption of serial data on bus
With 82B715, communication distance is extended to beyond 100
feet (30M)
80C51 8-bit microcontroller family
2K/64 OTP/ROM, 5 channel 8 bit A/D, I
EA
2
C bus uses two wires (SDA and SCL) to transfer information
2
C data, I
EAD
EA
EAD
ETI
ES
EPWM
EX1
ET0
EX0
2
C subsystem includes hardware to simplify the
2
2
C compatible ICs is available. See the I
C status, and I
ETI
2
Global interrupt disable when EA = 0
A/D conversion complete
Timer I
I
PWM counter overflow
External interrupt 1
Timer 0 overflow
External interrupt 0
2
C serial port is a single bit hardware
C serial port
2
Function
C serial communications port instead of
ES
2
C bus. This circuitry is the same as
2
C configuration.
EPWM
EX1
ET0
2
C section
2
C
2
EX0
2
C, PWM, low pin count
C
LSB
8
Pulse Width Modulation Output (P0.4)
The PWM outputs pulses of programmable length and interval. The
repetition frequency is defined by an 8-bit prescaler which generates
the clock for the counter. The prescaler register is PWMP. The
prescaler and counter are not associated with any other timer. The
8-bit counter counts modulo 255, that is from 0 to 254 inclusive. The
value of the 8-bit counter is compared to the contents of a compare
register, PWM. When the counter value matches the contents of this
register, the output of the PWM is set high. When the counter reaches
zero, the output of the PWM is set low. The pulse width ratio (duty
cycle) is defined by the contents of the compare register and is in the
range of 0 to 1 programmed in increments of 1/255. The PWM output
can be set to be continuously high by loading the compare register
with 0 and the output can be set to be continuously low by loading the
compare register with 255. The PWM output is enabled by a bit in a
special function register, PWENA. When enabled, the pin output is
driven with a fully active pull-up. That is, when the output is high, a
strong pull-up is continuously applied. when disabled, the pin
functions as a normal bidirectional I/O pin, however, the counter
remains active.
The PWM function is disabled during RESET and remains disabled
after reset is removed until re-enabled by software. The PWM output
is high during power down and idle. The counter is disabled during
idle. The repetition frequency of the PWM is given by:
The low/high ratio of the PWM signal is PWM / (255 – PWM) for
PWM not equal to 255. For PWM = 255, the output is always low.
The repetition frequency range is 92Hz to 23.5kHz for an oscillator
frequency of 12 MHz.
An interrupt will be asserted upon PWM counter overflow if the
interrupt is not masked off.
The PWM output is an alternative function of P0.4. In order to use
this port as a bidirectional I/O port, the PWM output must be
disabled by clearing the enable/disable bit in PWENA. In this case,
the PWM subsystem can be used as an interval timer by enabling
the PWM interrupt.
f
PWM
= f
OSC
/ 2 (1 + PWMP) 255
83C752/87C752
Product specification