ATA5773-DK1 Atmel, ATA5773-DK1 Datasheet - Page 80

• Manufacturer Part Number: ATA5773-DK1
• Description: BOARD XMITTER FOR ATA5773 315MHZ
• Manufacturer: Atmel
• Type: Transmitterr

Specifications of ATA5773-DK1

• Frequency: 315MHz
• Maximum Frequency: 315 MHz
• Supply Voltage (max): 4 V
• Supply Voltage (min): 2 V
• Supply Current: 9 mA
• Product: RF Development Tools
• For Use With/related Products: ATA5773
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.15.5.1
4.15.5.2
4.15.5.3
4.15.6
80
Atmel ATA5771/73/74
Compare Match Output Unit
Force Output Compare
Compare Match Blocking by TCNT0 Write
Using the Output Compare Unit
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 COM0x1:0 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
initialized 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 equals the OCR0x value, the Compare Match will be missed, resulting in incorrect
waveform generation. Similarly, do not write the TCNT0 value equal to BOTTOM when the
counter is down-counting.
The setup of the OC0x should be performed before setting the Data Direction Register for the
port pin to output. The easiest way of setting the OC0x value is to use the Force Output Com-
pare (0x) strobe bits in Normal mode. The OC0x Registers keep their values even when
changing between Waveform Generation modes.
Be aware that the COM0x1:0 bits are not double buffered together with the compare value.
Changing the COM0x1:0 bits will take effect immediately.
The Compare Output mode (COM0x1:0) bits have two functions. The Waveform Generator
uses the COM0x1:0 bits for defining the Output Compare (OC0x) state at the next Compare
Match. Also, the COM0x1:0 bits control the OC0x pin output source.
shows a simplified schematic of the logic affected by the COM0x1:0 bit setting. The I/O Regis-
ters, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the general I/O Port
Control Registers (DDR and PORT) that are affected by the COM0x1:0 bits are shown. When
referring to the OC0x state, the reference is for the internal OC0x Register, not the OC0x pin.
If a system reset occur, the OC0x Register is reset to “0”.
Figure 4-29 on page 81
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