upd17072 Renesas Electronics Corporation., upd17072 Datasheet - Page 86

• Manufacturer Part Number: upd17072
• Description: 4-bit Single-chip Microcontroller With Hardware For Digital Tuning System
• Manufacturer: Renesas Electronics Corporation.

12.2.5 Notes on using basic timer 0
86
(1) BTM0CY flag detection time interval
(2) Sum of timer updating processing time and BTM0CY flag detection time interval
The time interval at which the BTM0CY flag is to be detected must be shorter than the time interval at which
the flag is to be set. This is because, if the time of processing B in Figure 12-4 is longer than the time interval
at which the BTM0CY flag is to be set, the BTM0CY flag is not set accurately.
As described in (1) above, the time interval t
than the time at which the BTM0CY flag is to be set.
At this time, even if the time interval at which the BTM0CY flag is to be detected is short, the timer processing
may not be executed normally when CE reset is effected if the updating processing time of the timer is long.
Therefore, the following conditions must be satisfied:
An example is shown below.
BTM0CY flag
setting pulse
BTM0CY flag
t
CHECK
+ t
where,
t
t
t
CHECK
TIMER
SET
TIMER
: time interval at which BTM0CY flag is set
: timer updating processing time
: time interval at which BTM0CY flag is detected
< t
H
L
1
0
Figure 12-4. Detection of BTM0CY Flag and BTM0CY Flag
SET
<1>
SKT1
BTM0CY
Because execution time of processing B is too long after BTM0CY
flag, which has been set to "1" in step <2> above, has been
detected, BTM0CY flag is not detected in step <3>.
Processing A
CHECK
<2>
at which the BTM0CY flag is to be detected must be shorter
SKT1
BTM0CY
Processing B
<3>
<4>
SKT1
BTM0CY
PD17072,17073
<5>