218
8331B–AVR–03/12
Atmel AVR XMEGA AU
The hi-res extension will not output any pulse shorter than one peripheral clock cycle; i.e., a
compare value lower than four will have no visible output.
17.3
Register Description
17.3.1
CTRLA – Control register A
• Bit 7:3 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always
write these bits to zero when this register is written.
• Bit 2 – HRPLUS: High Resolution Plus
Setting this bit enables high resolution plus. Hi-res plus is the same as hi-res, but will increase
the resolution by eight (3 bits) instead of four.
The extra resolution is achieved by operating at both edges of the peripheral 4x clock.
• Bit 1:0 – HREN[1:0]: High Resolution Enable
These bits enables the high-resolution mode for a timer/counter according to
Setting one or both HREN bits will enable high-resolution waveform generation output for the
entire general purpose I/O port. This means that both timer/counters connected to the same port
must enable hi-res if both are used for generating PWM or FRQ output on pins.
17.4
Register Summary
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
HRPLUS
HREN[1:0]
CTRLA
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Table 17-1.
High Resolution Enable
HREN[1:0]
High Resolution Enabled
00
None
01
Timer/counter 0
10
Timer/counter 1
11
Both timer/counters
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Page
+0x00
CTRLA
–
–
–
–
–
HRPLUS
HREN[1:0]