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CHAPTER 7 16-bit I/O timer
7.2.1
Block Diagram of 16-bit Free-run Timer
The 16-bit free-run timer consists of the following blocks:
• Prescaler
• Timer counter data register (TCDT)
• Timer counter control status register (TCCS)
I Block Diagram of 16-bit Free-run Timer
φ
Prescaler
3
Timer counter control
status register
(TCCS)
φ
: Machine clock
OF
: Over flow
I Details of Pins in Block Diagram
The 16-bit I/O timer contains one 16-bit free-run timer.
The interrupt request number of the 16-big free-run timer is as follows:
Interrupt request number: 19 (13
G
Prescaler
The prescaler divides the frequency of the machine clock to supply a count clock to the 16-bit up counter.
Any of four machine clock division ratios are selected by setting the timer counter control status register
(TCCS).
G
Timer counter data register (TCDT)
The timer counter data register (TCDT) is a 16-bit up counter.At read, the current count value of the 16-bit
free-run timer can be read.Writing while the counter is stopped enables any count value to be set.
222
Figure 7.2-2 Block Diagram of 16-bit Free-run Timer
Timer counter data register
(TCDT)
16-bit free-run timer
OF
CLK
STOP
IVF
IVFE
STOP
CLR
Reserved
)
H
CLR
CLK2 CLK1 CLK0
Output count value
to input capture
Free-run timer
interrupt request
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