C8051F045 View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F045

Mixed Signal ISP Flash MCU Family

Silicon Laboratories 

C8051F040/1/2/3/4/5/6/7

24.2.4. 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 24.1, where FPCA is the fre-

quency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD.

Equation 24.1. Square Wave Frequency Output

Fsqr = 2----------P----C-F---A-P---C0---A-C----P----H-----n-

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

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. 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 24.7. PCA Frequency Output Mode

Rev. 1.5

309

Share Link: