
R01UH0336EJ0102 Rev.1.02
Page 261 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 7 Clock Generation
7.5 Clock Output Function (CLKOUT)
The clock-output function handles the output of a clock signal from CLKOUT
pin. The signal for output from the CLKOUT pin can be frequency-divided by
the baud-rate generator.
The figure below is a schematic view of the clock output function.
7.5.1
Baud-Rate Generator for CLKOUT Function (BRGA)
The baud-rate generator frequency-divides the clock signal it receives as input
and can thus produce clock signals at various frequencies on the CLKOUT pin.
BRGA0 inverts the output signal on CLKOUT when the value of the baud-rate
counter matches the setting of the BRGA0CMP[7:0] bits in the BRGA0CMP
register. If BRGA0CTL.BRGA0ODIS = 1, the low level is output on CLKOUT.
When the counter reaches the value for comparison set in
BRGA0CMP.BRGA0CMP[7:0], the BRGA0 interrupt (INTBRG0) is generated.
Note
When BRGA0CMP.BRGA0CMP[7:0] = 00
H
, the initial counting value is 01
H
,
and the sequence of counting is 02
H
, 03
H
, ... FE
H
, FF
H
, 00
H
. Comparison after
the overflow of the counter overflows produces a match.
Calculating the
period of the signal
from the baud-rate
generator
• For BRGA0CMP.BRGA0CMP[7:0] = 00
H
, the period of the output clock
signal (CLKOUT) from the baud-rate generator is calculated from:
CLKOUT period = counter clock cycle
256
2
• For BRGA0CMP.BRGA0CMP[7:0] = N = 01
H
to FF
H
, the period of the
output clock signal (CLKOUT) from the baud-rate generator is calculated
from:
CLKOUT period = counter clock cycle
N
2
CLKOUT pin
BRGA0TCLK
Prescaler
(f/1, f/2, f/4, f/8)
8-bit
counter
BRGA0CMP
[7:0]
BRG output
controller
INTBRG0