21.5.2 Control B - Normal Mode


Bit	7	6	5	4	3	2	1	0
		CMP2EN	CMP1EN	CMP0EN	ALUPD	WGMODE[2:0]
Access		R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset		0	0	0	0	0	0	0

Bits 4, 5, 6 – CMPEN Compare n Enable

In the FRQ and PWM Waveform Generation modes, the Compare n Enable (CMPnEN) bits will make the waveform output available on the pin corresponding to WOn, overriding the value in the corresponding PORT output register. The corresponding pin direction must be configured as an output in the PORT peripheral.

Value	Description
0	Waveform output WOn will not be available on the corresponding pin
1	Waveform output WOn will override the output value of the corresponding pin

Bit 3 – ALUPD Auto-Lock Update

The Auto-Lock Update bit controls the Lock Update (LUPD) bit in the TCAn.CTRLE register. When ALUPD is written to ‘1’, the LUPD bit will be set to ‘1’ until the Buffer Valid (CMPnBV) bits of all enabled compare channels are ‘1’. This condition will clear the LUPD bit.

It will remain cleared until the next UPDATE condition, where the buffer values will be transferred to the CMPn registers, and the LUPD bit will be set to ‘1’ again. This makes sure that the CMPnBUF register values are not transferred to the CMPn registers until all enabled compare buffers are written.

Value	Description
0	LUPD bit in the TCAn.CTRLE register is not altered by the system
1	LUPD bit in the TCAn.CTRLE register is set and cleared automatically

Bits 2:0 – WGMODE[2:0] Waveform Generation Mode

This bit field selects the Waveform Generation mode and controls the counting sequence of the counter, TOP value, UPDATE condition, Interrupt condition, and the type of waveform generated.

No waveform generation is performed in the Normal mode of operation. For all other modes, the waveform generator output will only be directed to the port pins if the corresponding CMPnEN bit has been set. The port pin direction must be set as output.

Table 21-7. Timer Waveform Generation Mode
Value	Group Configuration	Mode of Operation	TOP	UPDATE	OVF
`0x0`	NORMAL	Normal	PER	TOP⁽¹⁾	TOP⁽¹⁾
`0x1`	FRQ	Frequency	CMP0	TOP⁽¹⁾	TOP⁽¹⁾
`0x2`	-	Reserved	-	-	-
`0x3`	SINGLESLOPE	Single-slope PWM	PER	BOTTOM	BOTTOM
`0x4`	-	Reserved	-	-	-
`0x5`	DSTOP	Dual-slope PWM	PER	BOTTOM	TOP
`0x6`	DSBOTH	Dual-slope PWM	PER	BOTTOM	TOP and BOTTOM
`0x7`	DSBOTTOM	Dual-slope PWM	PER	BOTTOM	BOTTOM

Note:

When counting up.

Name:	CTRLB
Offset:	0x01
Reset:	0x00
Property:	-

ATtiny3224/3226/3227

21.5.2 Control B - Normal Mode

Bits 4, 5, 6 – CMPEN Compare n Enable

Bit 3 – ALUPD Auto-Lock Update

Bits 2:0 – WGMODE[2:0] Waveform Generation Mode