C8051F020 View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F020

8K ISP FLASH MCU Family

Silicon Laboratories 

C8051F020/1/2/3

23.2.4. Frequency Output Mode

Frequency Output Mode produces a programmable-frequency square wave on the module’s associated CEXn pin.

The capture/compare module high byte holds the number of PCA clocks to count before the output is toggled. The

frequency of the square wave is then defined by Equation 23.1.

Equation 23.1. Square Wave Frequency Output

FCEXn

=

---------------F----P---C---A---------------

2 × PCA0CPHn

Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.

Where FPCA is the frequency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD. The

lower byte of the capture/compare module is compared to the PCA0 counter low byte; on a match, CEXn is toggled

and the offset held in the high byte is added to the matched value in PCA0CPLn. Frequency Output Mode is enabled

by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register.

Write to

PCA0CPLn

0

ENB

Reset

Write to

PCA0CPHn ENB

1

Figure 23.7. PCA Frequency Output Mode

PCA0CPMn

P ECCMT P E

WCAA AOWC

MOP P TGMC

1 MPN n n n F

6nnn

n

n

x 000 x

PCA0CPLn

Enable

8-bit

Comparator

8-bit Adder

PCA0CPHn

Adder

Enable

Toggle

match

TOGn

0 CEXn Crossbar

1

Port I/O

PCA Timebase

PCA0L

256

Rev. 1.4

Share Link: