C8051F521A-IM View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F521A-IM

8/4/2 kB ISP Flash MCU Family

Silicon Laboratories 

C8051F52x/F53x

19.2.4. 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 out-

put is toggled. The frequency of the square wave is then defined by Equation 19.1.

FCEXn

=

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

2  PCA0CPHn

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

Equation 19.1. Square Wave Frequency Output

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 PCA 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. Fre-

quency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register.

PCA0CPMn

P ECCMT P E

WCA A AOWC

MOPP TGMC

1 MPN n n n F

6nnn

n

n

0 0001 0

PCA0CPLn

Enable

8-bit

Comparator

8-bit Adder

PCA0CPHn

Adder

Enable

Toggle

match

TOGn

0 CEXn Crossbar

1

Port I/O

PCA Timebase

PCA0L

Figure 19.7. PCA Frequency Output Mode

Rev. 1.4

201

Share Link: