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DS30575A-page 482  2012 Microchip Technology Inc.

EXAMPLE 22-6: CONVERTING A SINGLE CHANNEL, ONCE PER INTERRUPT, DUAL BUFFER

MODE

22.8.3.1 Using Alternating MUX A and MUX

B Input Selections

Figure 22-19 and Example 22-7 demonstrate alternate

sampling of the inputs assigned to MUX A and MUX B.

Setting the ALTS bit enables alternating input selec-

tions. The first sample uses the MUX A inputs specified

by the CH0SAx and CH0NAx bits. The next sample

uses the MUX B inputs, specified by the CH0SBx and

CH0NBx bits.

This example also demonstrates use of the dual,

8-word buffers. An interrupt occurs after every 8th

sample, resulting in filling eight words into the buffer on

each interrupt.

A/D Configuration:

• Select AN3 for S/H+ Input (CH0SA<4:0> = 00011)

•Select V

R- for S/H- Input (CH0NA<2:0> = 000)

• Configure for No Input Scan (CSCNA = 0)

• Use Only MUX A for Sampling (ALTS = 0)

• Set AD1IF on Every Sample (SMPI<4:0> = 00000)

• Configure Buffer as Dual, 8-Word Segments (BUFM = 1)

Operational Sequence:

1. Sample MUX A Input, AN3; Convert and Write to Buffer 0h.

2. Set AD1IF Flag (and generate interrupt, if enabled); Write Access Automatically

Switches to Alternate Buffer.

3. Sample MUX A Input, AN3; Convert and Write to Buffer 8h.

4. Set AD1IF Flag (and generate interrupt, if enabled); Write Access Automatically

Switches to Alternate Buffer.

5. Repeat (1-4).

Results Stored in Buffer (after 2 cycles):

Buffer

Address

Buffer Contents

at 1st AD1IF Event

Buffer Contents

at 2nd AD1IF Event

ADC1BUF0 Sample 1 (AN3, Sample 1) (undefined)

ADC1BUF1 (undefined) (undefined)

ADC1BUF2 (undefined) (undefined)

ADC1BUF3 (undefined) (undefined)

ADC1BUF4 (undefined) (undefined)

ADC1BUF5 (undefined) (undefined)

ADC1BUF6 (undefined) (undefined)

ADC1BUF7 (undefined) (undefined)

ADC1BUF8 (undefined) Sample 2 (AN3, Sample 2)

ADC1BUF9 (undefined) (undefined)

ADC1BUFA (undefined) (undefined)

ADC1BUFB (undefined) (undefined)

ADC1BUFC (undefined) (undefined)

ADC1BUFD (undefined) (undefined)

ADC1BUFE (undefined) (undefined)

ADC1BUFF (undefined) (undefined)