EM78P330 datasheet(79/112 Pages) EMC

79 / 112 page

EM78P330/331N

8-Bit Microprocessor with OTP ROM

Product Specification (V 1.1) 03.13.2007

• 73

(This specification is subject to change without further notice)

Period

Duty Cycle

DT1 = TMR1

PRD1 = TMR1

Fig. 6-22 PWM Output Timing

6.10.2

Increment Timer Counter (TMRX: TMR1H/TWR1L, TMR2H

/TWR2L, or TMR3H/TWR3L)

TMRX are 10-bit clock counters with programmable prescalers. They are designed for

the PWM module as baud rate clock generators. TMRX can be read only. If employed,

they can be turned off for power saving by setting the T1EN bit [Bank 1 R5 <3>], T2EN

bit [Bank 1 R6 <7>] or T3EN bit [Bank 1 R6 <3>] to 0.

6.10.3 PWM Time Period (PRDX : PRD1 or PRD2 or PRD3)

The PWM time period is defined by writing to the PRDX register. When TMRX is equal

to PRDX, the following events occur on the next increment cycle:

TMRX is cleared

The PWMX pin is set to 1

The PWM duty cycle is latched from DT1/DT2/DT3 to DL1/DL2/DL3

NOTE

The PWM output will not be set, if the duty cycle is 0.

The PWMXIF pin is set to 1

The following formula describes how to calculate the PWM time period:

PERIOD = (PRDX + 1) * (1/Fosc) * CLKS/2 * (TMRX prescale value )

Example:

PRDX=49; Fosc=4MHz; CLKS bit of Code Option Register =0 (2

oscillator periods); TMRX (0, 0, 0) = 1:2, then PERIOD=(49 + 1) *

(1/4M) * 2/2 * 2 = 25us

EM78P330 Datasheet(PDF) 79 Page - ELAN Microelectronics Corp