MC68HC05E0 Datasheet, PDF (61/96 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor (HCMOS) microcontroller unit

7
TIMERS
The MC68HC05E0 contains three timers: Timer A, Timer B and the Real Time Interrupt Timer.
Timers A and B are driven by the sub-system clock, which also drives the Serial Interface
sub-system. The Real Time Interrupt timer is driven from the bus clock (P02).
Timer A and Timer B can generate an independent interrupt signal to the processor. Timer A has
a higher interrupt priority than timer B. The Real Time Interrupt shares its interrupt vector with the
External Interrupt (INTX) and the Port C Wake-up function.
7
7.1
Sub-system Clock Control
The sub-system clock frequency f_sub is generated from the bus clock frequency (P02) by a
selectable prescaler (see Figure 7-1).
Bus Clock
Frequency
P02
÷2
÷2
÷2
Sub-system
Clock
Frequency
f sub
00
01
MUX
10
11
TS (Timer Stop Gate Input Pin)
Timer A
Timer B
SI
Timer Control Register ($000C) SC1 SC0
CETB CETA
Figure 7-1 Sub-system Clock Generation
RTI Timer
MC68HC05E0
TIMERS
MOTOROLA
7-1