Zilog Z08470 - Manual (Page 23)

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UM008101-0601 Counter/Timer Channels
The Prescaler
The prescaler is an 8-bit device that is used in the TIMER mode only. The
prescaler is programmed by the CPU through the Channel Control register
to divide its input, the System clock (0), by 16 or 256. The output of the
prescaler is then fed as an input to clock the down-counter. Each time that
Table 2. Channel Control Register
7 6 5 4 3 2 1 0
Interrupt Mode Prescaler
Value* CLK/TRG
Section Time
Trigger* Time
Constant Reset Control or
Vector
R/W R/W R/W R/W R/W R/W R/W R/W
Bit Number Field R/W Value Description
7 Interrupt R/W 1
0 Enable Interrupt
Disable Interrupt
6 Mode R/W 1
0 COUNTER Mode
TIMER Mode
5 Prescaler Value* R/W 1
0 256
16
4 CLK/TRG Edge
Section R/W 1
0 Rising Edge
Falling Edge
3 Time Trigger* R/W 1
0 CLK/TRG Pulse Starts Timer
Automatic trigger when time constant is loaded
2 Time Constant R/W 1
0 Time Constant Follows
No Time Constant Follows
1 Reset R/W 1
0 Software Reset
Continue Operation
0 Control or Vector R/W 1
0 Control
Vector
*TIMER mode only