P8XCL580HFT View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'P8XCL580HFT' PDF : 80 Pages View PDF
Philips Semiconductors
Low voltage 8-bit microcontrollers with
UART, I2C-bus and ADC
Product specification
P80CL580; P83CL580
12 PULSE WIDTH MODULATED OUTPUT
One Pulse Width Modulated output channel (PWM0) is
provided which outputs pulses of programmable length
and interval. The repetition frequency is defined by an 8-bit
prescaler (PWMP) that generates the clock for the
counter. The 8-bit counter counts modulo 255, i.e. from
0 to 254 inclusive. The value held in the 8-bit counter is
compared to the contents of the register PWM0.
Provided the contents of this register are greater than the
counter value, the PWM0 output is set LOW. If the
contents of register PWM0 are equal to, or less than the
counter value, the PWM0 output is set HIGH.
The pulse-width-ratio is therefore defined by the contents
of register PWM0. The pulse-width-ratio will be in the
range 0 to 255⁄255 and may be programmed in increments
of 1⁄255.
The repetition frequency (fPWM) at the PWM0 output is
given by:
fPWM = -{----2------×------(--1------+-----P----f-W-o---s--Mc-----P------)----×-----2---5----5-----}---
For fosc = 12 MHz the above formula gives a repetition
frequency range of 92 Hz to 23.5 kHz.
By loading the PWM0 register with either 00H or FFH, the
PWM0 output can be retained at a constant HIGH or LOW
level respectively. When loading FFH into the PWM0
register, the 8-bit counter will never actually reach this
value.
The PWM0 output pin is driven by push-pull drivers and is
not shared with any other function.
12.1 Prescaler Frequency Control Register (PWMP)
Table 5 Prescaler Frequency Control Register (address FEH)
7
PWMP.7
6
PWMP.6
5
PWMP.5
4
PWMP.4
3
PWMP.3
2
PWMP.2
1
PWMP.1
Table 6 Description of PWMP bits
BIT
7 to 1
SYMBOL
PWMP.7 to PWMP.0
DESCRIPTION
Prescaler division factor = (PWMP) + 1.
12.2 Pulse Width Register (PWM0)
Table 7 Pulse Width Register (address FCH)
7
PWM0.7
6
PWM0.6
5
PWM0.5
4
PWM0.4
3
PWM0.3
2
PWM0.2
1
PWM0.1
Table 8 Description of PWM0 bits
BIT
SYMBOL
7 to 1
PWM0.7 to PWM0.0
DESCRIPTION
LOW/HIGH ratio of PWM0 signal = -{----2---5----5--(--–-P----W-(--P---M--W--0----M)-----0----)---}---
0
PWMP.0
0
PWM0.0
1997 Mar 14
21
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