Timer A
This version of timer is included in the H8/3814 Series, the H8/3834 Series, the H8/3877
Series, and the H8/3927 Series microcomputers.
Function: Timer A is an 8-bit interval timer that can also be used as a clock time base.
Features: • The timer A clock can be selected from eight internal clock frequencies
(ø/8192, ø/4096, ø/2048, ø/512, ø/256, ø/128, ø/32, and ø/8).
• Four overflow periods (2, 1, 0.5, and 0.125 seconds when used at 32.768 kHz)
available when used as a clock time base.
• Generates a counter overflow interrupt.
• A clock with one of eight periods (ø/32, ø/16, ø/8, ø/4, ø
and ø
Block Diagram
ø
(32 kHz)
W
Clock output
TMOW
System clock ø
<Notation>
TMA:
Timer mode register A
TCA:
Timer counter A
IRRTA:
Timer A overflow interrupt request flag
Notes: 1.
* These can only be selected when the prescaler W output (ø
clock.
2.
This figure shows the Timer A circuit used in the H8/3834.
/4) can be output from the TMOW pin.
W
ø
/4
W
1/4
Prescaler W
ø
/32, ø
/8,
W
W
ø
/16, ø
/4
W
W
ø/32, ø/8,
ø/16, ø/4
Prescaler S
ø
/256
W
ø/8192, ø/4096,
ø/2048, ø/512, ø/256,
ø/128, ø/32, ø/8
81
Peripheral Functions
/32, ø
/16, ø
W
W
TMA
TCA
/128) is used as the TCA input
W
/8,
W
IRRTA