# 5.3 Left Adjust

The Left Adjust (LEFTADJ) bit in the Control F (ADCn.CTRLF) register enables left-shift of the output data in the modes where this is supported. If enabled, this will left-shift the output from both the Result and the Sample registers. It is configured as shown in the following code snippet:

ADC0.CTRLF = ADC_LEFTADJ_bm;/* Enable Left Adjust bit */

Left adjust is available in ADC mode 3, Series Accumulation with Scaling.

The following tables show how the left adjust feature affects the Result register output format in Single-Ended and Differential modes.

LEFTADJ | RES[31:24] | RES[23:16] | RES[15:12] | RES[11:8] | RES[7:0] |
---|---|---|---|---|---|

0 | 0x00 | Scaled accumulation[15:0] | |||

1 | 0x00 | Scaled
accumulation[15:0]^{(1)} |

LEFTADJ | RES[31:24] | RES[23:16] | RES[15:12] | RES[11:8] | RES[7:0] |
---|---|---|---|---|---|

0 | Sign Extension | Signed Scaled accumulation[15:0] | |||

1 | Sign Extension | Signed
Scaled accumulation[15:0]^{(1)} |

If SAMPNUM < 4, the result is left-shifted 4 - SAMPNUM bits such that bit 15 is the MSb. If SAMPNUM > 4, the scaling feature of the ADC mode right-shifts the result by SAMPNUM - 4 bits.

**Example 1: SAMPNUM = 3 (Accumulation with 8 samples)**

When the Left Adjust bit is 0, ADCn.SAMPLE = `0xFFF`

for all
samples, and 8 samples are accumulated, the accumulated value in ADCn.RESULT is 8 x 4095
= `0x7FF8`

.

After enabling the Left Adjust bit, the result will be left-shifted by 4 -
SAMPNUM = 1 bit (SAMPNUM is 3 to accumulate 8 samples). So by left-shifting
`0x7FF8`

by 1 bit, ADCn.RESULT = `0xFFF0`

.

**Example 2: SAMPNUM = 5 (Accumulation with 32 samples)**

When the Left Adjust bit is 0, ADCn.SAMPLE = `0xFFF`

for all
samples, and 32 samples are accumulated, the accumulated value is 32 x 4095 =
`0x1FFE0`

.

In Scaling mode, the result will be right-shifted by SAMPNUM - 4 = 1 bit
(SAMPNUM is 5 to accumulate 32 samples). So by right-shifting `0x1FFE0`

by 1 bit, ADCn.RESULT = `0xFFF0`

.

The following table show how the left adjust feature affects the Sample register output format in Single-Ended and Differential modes.

LEFTADJ | DIFF | SAMPLE[15:12] | SAMPLE[11:8] | SAMPLE[7:0] |
---|---|---|---|---|

0 | 0 | 0x00 | Conversion[11:0] | |

1 | Sign extension | Signed conversion[11:0] | ||

1 | 0 | Conversion[11:0] << 4 | ||

1 | Signed conversion[11:0] << 4 |

For example, if the Left Adjust feature is disabled and the ADCn.SAMPLE
value is `0x0FFF`

, the corresponding ADCn.SAMPLE value when Left Adjust
is enabled is `0xFFF0`

.