Datasheet

87
8183F–AVR–06/12
ATtiny24A/44A/84A
12.2.3 Compatibility
The 16-bit Timer/Counter has been updated and improved from previous versions of 16-bit AVR
Timer/Counter. This 16-bit Timer/Counter is fully compatible with the earlier version regarding:
• All 16-bit Timer/Counter related I/O Register address locations, including Timer Interrupt
Registers.
• Bit locations inside all 16-bit Timer/Counter Registers, including Timer Interrupt Registers.
• Interrupt Vectors.
The following control bits have been renamed, but retained the same functionality and register
locations:
• PWM10 is changed to WGM10.
• PWM11 is changed to WGM11.
• CTC1 is changed to WGM12.
The following bits have been added to the 16-bit Timer/Counter Control Registers:
• 1A and 1B are added to TCCR1A.
• WGM13 is added to TCCR1B.
The 16-bit Timer/Counter has improvements that will affect backward compatibility in some spe-
cial cases.
12.3 Timer/Counter Clock Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock source
is selected by the Clock Select logic which is controlled by the Clock Select (CS1[2:0]) bits
located in the Timer/Counter control Register B (TCCR1B). For details on clock sources and
prescaler, see “Timer/Counter Prescaler” on page 113.
12.4 Counter Unit
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit.
Figure 12-2 shows a block diagram of the counter and its surroundings.
Figure 12-2. Counter Unit Block Diagram
TEMP (8-bit)
DATA BU S (8-bit)
TCNTn (16-bit Counter)
TCNTnH (8-bit) TCNTnL (8-bit)
Control Logic
Count
Clear
Direction
TOVn
(Int.Req.)
Clock Select
TOP BOTTOM
Tn
Edge
Detector
( From Prescaler )
clk
Tn