Microcontroller
Peripheral Timing
Calculator

Philips 87LPC768 - Pulse Width Modulator

Recommended books:

The 8051 Microcontroller

Enter the clock frequency being used and the values assigned to the PWM SFRs.
If a channel is not being used then leave its associated SFRs blank.

Valid notation for SFR values:

Binary: 00010010B, 10010010b
Hexadecimal: 0x3D, 3DH, 3Dh

Register Values
Counter Reload Value (CNSW)	cnsw = cnsw0 + (cnsw1<<8)
Channel 0 Compare Value (CPSW)	cpsw00 = cpsw0 + ((cpsw4 & 0x03)<<8)
Channel 1 Compare Value (CPSW)	cpsw01 = cpsw1 + (((cpsw4>>2) & 0x03)<<8)
Channel 2 Compare Value (CPSW)	cpsw02 = cpsw2 + (((cpsw4>>4) & 0x03)<<8)
Channel 3 Compare Value (CPSW)	cpsw03 = cpsw3 + (((cpsw4>>6) & 0x03)<<8)

Clock Period, PWM Period, Pulse Lengths and Duty Cycles
	6-clock Mode (UCFG1.3 = 1)	12-clock Mode (UCFG1.3 = 0)
PWM Counter Clock Period (us)	tpwmclk6 = 1/fclk	tpwmclk12 = 2/fclk
Period (us)	tp6 = tpwmclk6 x (cnsw + 1)	tp12 = tpwmclk12 x (cnsw + 1)
Channel 0 Pulse Length (us)	tpulse06 = (cnsw - cpsw06 + 1) x tpwmclk6	tpulse012 = (cnsw - cpsw012 + 1) x tpwmclk12
Channel 1 Pulse Length (us)	tpulse16 = (cnsw - cpsw16 + 1) x tpwmclk6	tpulse112 = (cnsw - cpsw112 + 1) x tpwmclk12
Channel 2 Pulse Length (us)	tpulse26 = (cnsw - cpsw26 + 1) x tpwmclk6	tpulse212 = (cnsw - cpsw212 + 1) x tpwmclk12
Channel 3 Pulse Length (us)	tpulse36 = (cnsw - cpsw36 + 1) x tpwmclk6	tpulse312 = (cnsw - cpsw312 + 1) x tpwmclk12
Channel 0 Duty Cycle (%)	dcycle06 = tpulse06/tp6 x 100	dcycle012 = tpulse012/tp12 x 100
Channel 1 Duty Cycle (%)	dcycle16 = tpulse16/tp6 x 100	dcycle112 = tpulse112/tp12 x 100
Channel 2 Duty Cycle (%)	dcycle26 = tpulse26/tp6 x 100	dcycle212 = tpulse212/tp12 x 100
Channel 3 Duty Cycle (%)	dcycle36 = tpulse36/tp6 x 100	dcycle312 = tpulse312/tp12 x 100

Upcoming Classes

� ESAcademy, 2000
Author: Andrew Ayre

All materials
provided 'as is'
see Disclaimer