ATTINY20-EK1 Atmel, ATTINY20-EK1 Datasheet - Page 63

• Manufacturer Part Number: ATTINY20-EK1
• Description: KIT EVAL TOUCH ATTINY20
• Manufacturer: Atmel

Specifications of ATTINY20-EK1

• Sensor Type: *
• Sensing Range: *
• Interface: *
• Sensitivity: *
• Voltage - Supply: *
• Embedded: *
• Utilized Ic / Part: *
• Silicon Manufacturer: Atmel
• Core Architecture: AVR
• Core Sub-architecture: TinyAVR
• Kit Contents: Board
• Svhc: No SVHC (15-Dec-2010)
• Mcu Supported Families: ATtiny20
• Tool / Board Applications: Microcontroller
• Rohs Compliant: Yes
• Tool Type: Development Kit
• Cpu Core: AVR 8
• Data Bus Width: 8 bit
• Processor To Be Evaluated: ATtiny20
• Interface Type: Touch
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

11.5.1
11.5.2
11.5.3
8235B–AVR–04/11
Force Output Compare
Compare Match Blocking by TCNT0 Write
Using the Output Compare Unit
Figure 11-3 on page 63
Figure 11-3. Output Compare Unit, Block Diagram
The OCR0x Registers are double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of operation, the dou-
ble buffering is disabled. The double buffering synchronizes the update of the OCR0x Compare
Registers to either top or bottom of the counting sequence. The synchronization prevents the
occurrence of odd-length, non-symmetrical PWM pulses, thereby making the output glitch-free.
The OCR0x Register access may seem complex, but this is not case. When the double buffering
is enabled, the CPU has access to the OCR0x Buffer Register, and if double buffering is dis-
abled the CPU will access the OCR0x directly.
In non-PWM waveform generation modes, the match output of the comparator can be forced by
writing a one to the Force Output Compare (0x) bit. Forcing Compare Match will not set the
OCF0x Flag or reload/clear the timer, but the OC0x pin will be updated as if a real Compare
Match had occurred (the COM0x[1:0] bits settings define whether the OC0x pin is set, cleared or
toggled).
All CPU write operations to the TCNT0 Register will block any Compare Match that occur in the
next timer clock cycle, even when the timer is stopped. This feature allows OCR0x to be initial-
ized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter clock is
enabled.
Since writing TCNT0 in any mode of operation will block all Compare Matches for one timer
clock cycle, there are risks involved when changing TCNT0 when using the Output Compare
Unit, independently of whether the Timer/Counter is running or not. If the value written to TCNT0
top
bottom
FOCn
OCRnx
shows a block diagram of the Output Compare unit.
WAVEFORM GENERATOR
WGMn[2:0]
8-BIT COMPARATOR
DATA BUS
COMnX[1:0]
TCNTn
OCFnx (Int.Req.)
OCnx
ATtiny20
63