Frequency Output Mode; Figure 22.7. Pca Frequency Output Mode - Silicon Laboratories C8051F341 Product Manual

22.2.4. 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 22.1.
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Equation 22.1. Square Wave Frequency Output
Where F is the frequency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD.
PCA
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.
Write to
PCA0CPLn 0
ENB
Reset
Write to
PCA0CPHn ENB
1
C8051F340/1/2/3/4/5/6/7/8/9/A/B/C/D
---------------------------------------- -
F =

CEXn
2
PCA0CPMn
P P
E C C M T E
W W
C A A A O C
PCA0CPLn
M M
O P P T G C
1 n
M P N n n F
6
n n n n
n
x 0 0 0 x
8-bit
Enable
Comparator
PCA Timebase
PCA0L

Figure 22.7. PCA Frequency Output Mode

Rev. 1.3
F
PCA
PCA0CPHn
8-bit Adder
Adder
Enable
TOGn
Toggle
0
match
1
PCA0CPHn
CEXn
Crossbar Port I/O
261