Rainbow Electronics ATmega8HVD - Manual (Page 74)

74
8052B–AVR–09/08
ATmega4HVD/8HVD
16. Timer/Counter(T/C0,T/C1)
16.1 Features
• Clear Timer on Compare Match (Auto Reload)
• Input Capture unit
• Four Independent Interrupt Sources (TOVn, OCFnA, OCFnB, ICFn)
• 8-bit Mode with Two Independent Output Compare Units
• 16-bit Mode with One Independent Output Compare Unit
16.2 Overview
Timer/Counter n is a general purpose 8-/16-bit Timer/Counter module, with two/one Output
Compare units and Input Capture feature.
ATmega4HVD/8HVD has two Timer/Counters, Timer/Counter0 and Timer/Counter1. The
functionality for both Timer/Counters is described below. Timer/Counter0 and Timer/Counter1
have different Timer/Counter registers, as shown in
”Register Summary” on page 151 .
The Timer/Counter general operation is described in 8-/16-bit mode. A simplified block dia-
gram of the 8-/16-bit Timer/Counter is shown in
Figure 16-1 . CPU accessible I/O Registers,
including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register and bit
locations are listed in the
”Register Description” on page 86 .
Figure 16-1. 8-/16-bit Timer/Counter Block Diagram
Clock Select
Timer/Counter
D
ATA
B
U
S
OCRnB
=
TCNTnL
Noise
Canceler
ICPn0
=
Edge
Detector
Control Logic
TOP
Count
Clear
Direction
TOVn (Int. Req.)
OCnA (Int. Req.)
OCnB (Int. Req.)
ICFn (Int. Req.)
TCCRnA TCCRnB
Tn
Edge
Detector
( From Prescaler )
clk
Tn
=
OCRnA
TCNTnH
Fixed TOP value
ICPn1