Hardware manual

Rev. 3.0, 09/98, page 165 of 361
Bits 2, 1, and 0Clock Select (CKS2, CKS1, and CKS0): These bits and bits ICKS1 and
ICKS0 in the serial/timer control register (STCR) select the internal or external clock source for
the timer counter. Six internal clock sources, derived by prescaling the system clock, are available
for each timer channel. For internal clock sources the counter is incremented on the falling edge
of the internal clock. For an external clock source, these bits can select whether to increment the
counter on the rising or falling edge of the clock input, or on both edges.
TCR STCR
Channel
Bit 2
CKS2
Bit 1
CKS1
Bit 0
CKS0
Bit 1
ICKS1
Bit 0
ICKS0 Description
0 000No clock source (timer stopped) (Initial value)
0010φ/8 internal clock, counted on falling edge
0011φ/2 internal clock, counted on falling edge
0100φ/64 internal clock, counted on falling edge
0101φ/32 internal clock, counted on falling edge
0110φ/1024 internal clock, counted on falling edge
0111φ/256 internal clock, counted on falling edge
100No clock source (timer stopped)
101External clock source, counted on rising edge
110External clock source, counted on falling edge
111External clock source, counted on both rising and
falling edges
1 000No clock source (timer stopped) (Initial value)
0010φ/8 internal clock, counted on falling edge
0011φ/2 internal clock, counted on falling edge
0100φ/64 internal clock, counted on falling edge
0101φ/128 internal clock, counted on falling edge
0110φ/1024 internal clock, counted on falling edge
0111φ/2048 internal clock, counted on falling edge
100No clock source (timer stopped)
101External clock source, counted on rising edge
110External clock source, counted on falling edge
111External clock source, counted on both rising and
falling edges