Rev. 1.0, 02/00, page 780 of 1141
27.2.9
Noise Detection Level Register (NDETR)
0
0
0
0
0
0
0
0
7
W
NR0
0
W
NR7
6
W
NR6
5
W
NR5
4
W
NR4
3
W
NR3
2
W
NR2
1
W
NR1
Bit :
Initial value :
R/W :
The NDETR is an 8-bit write-only register for specifying the noise detection level. The set value
must be 1/4 of the actual noise detection level. The noise detection window signal is set to 1 at a
falling edge of the OSCH signal, and reset to 0 after the time specified by the HHK period setting
bits has passed. The OSCH signal falls about 5
µ
s after a rising edge of the SEPH signal.
When the noise detection counter value matches the specified noise detection level, the noise
detection interrupt request flag is set to 1. When reset, the NDETR is initialized to H'00. The
NDETR is assigned to the same address as the NDETC.
Figure 27.13 shows the timing for noise detection.
Csync
AFCV
NDETC
NDETR
SEPH
OSCH
NDETIF
HM
H complement and
mask counter
Cleared to 0 by CPU
Noise detection window
Noise
Noise
Noise
Noise
Noise counter
cleared
Noise
Comple-
ment
Comple-
ment
Noise
Pulse
lost
Pulse
lost
Figure 27.13 Noise Detection Window Setting and Noise Counting Timing