SM5902AF datasheet(26/40 Pages) NPC

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Compare-connect sequence

The SM5902AF supports three kinds of connect

modes; 3-pair compare-connect, 2-pair compare-

connect and direct connect.

Note that the SM5902AF can also operate in 12-bit

comparison connect mode using only the most sig-

nificant 12 bits of data for connection operation.

In 3-pair compare-connect mode, the final 6 valid

data (3 pairs of left- and right-channel data input

before encode processing) and the most recently

input data are compared until three continuous data

pairs all conform. At this point, the encode

sequence is re-started and data is written to VWA.

In 2-pair compare-connect mode, comparison

occurs just as for 3-pair comparison except that

only 2 pairs from the three compared need to con-

form with the valid data. At this point, the encode

sequence is re-started and data is written to VWA.

In direct-connect mode, comparison is not per-

formed at all, and encode sequence starts and data

is written to the VWA. This mode is for systems that

cannot perform compare-connect operation.

- Compare-connect preparation time

1. Comparison data preparation time

Internally, when the compare-connect start com-

mand is issued, a sequence starts to restore the

data for comparison. The time required for this

preparation after receiving the command is approxi-

mately 2.5

× (1/fs). (approximately 60 µs when fs =

44.1 kHz)

2. After the above preparation is finished, data is

input beginning from the left-channel data and com-

parison starts.

3. If the compare-connect command is issued

again, the preparation time above is not necessary

and operation starts from step 2.

4. The same sequence takes place in direct-con-

nect mode also. However, at the point when 3

words have been input, all data is directly connect-

ed as if comparison and conformance had taken

place.

- Compare-connect sequence stop

If a compare-connect stop command (80H with

MSDCN1= 1, MSDCN2= 0) is input from the micro-

controller, compare-connect sequence stops.

If compare-connect sequence was not operating,

the compare-connect stop command performs no

operation. However, make sure that the other bit

settings within the same 80H command are valid.

NIPPON PRECISION CIRCUITS-26

SM5902AF

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