AD2437 datasheet(4/42 Pages) AD

4 / 42 page

Rev. 0

Page 4 of 42

July 2023

AD2437

of a synchronization preamble. This preamble is followed by

control data to build a synchronization control frame (SCF).

Downstream, TDM synchronous data and SPI tunnel data are

added directly after the control frame. Every subordinate node

can use or consume some of the downstream data and add data

for downstream nodes. The last subordinate node transceiver

responds after the response time with a synchronization

response frame (SRF). Upstream TDM synchronous data and

SPI tunnel data are added by each node directly after the

response frame. Each node can also use or consume upstream

data.

The embedded control and response frames allow the host to

individually address each subordinate transceiver in the system.

The host also enables access to remote peripheral devices that

are connected to the subordinate transceivers via the I2C or SPI

ports for I2C to I2C, SPI to SPI, and SPI to I2C communication

over distance between multiple nodes.

All nodes in an A2B system are sampled synchronously in the

same A2B superframe. Synchronous I2S/TDM downstream data

from the nodes arrives at all downstream subordinate nodes in

the same A2B superframe, and every node’s upstream audio data

arrives synchronously in the same I2S/TDM frame at any

upstream node. I2S/TDM to I2S/TDM communication over dis-

tance does not require involvement of the main node and can be

performed directly between subordinate nodes. The remaining

audio phase differences between subordinate nodes can be com-

pensated for by register-programmable fine adjustment of the

SYNC pin signal delay.

There is a sample delay incurred for data moving between the

A2B bus and the I2S/TDM interfaces because data is received

and transmitted over the I2S/TDM every sample period (typi-

cally 48 kHz). This timing relationship between samples over

the A2B bus is shown in Figure 4. It shows the data transfer

between the main node and a subordinate node, but would be

similar for data transfer between any two subordinate nodes as

well.

Figure 3. A2B Superframe

Figure 4. A2B Bus Synchronous Data Exchange

SYNCH

CONTROL

FRAME

DOWNSTREAM

A2B DATA SLOTS

SYNCH

RESPONSE

FRAME

UPSTREAM

A2B DATA SLOTS

SYNCH

CONTROL

FRAME

SUPERFRAME: 20.83 s FOR 48kHz SAMPLING RATE

MAIN NODE

I2S TX

DATA

I2S RX

DATA

A2B DATA

I2S UPSTREAM DATA N - 2

SUB NODE

I2S UPSTREAM DATA N - 1I2S UPSTREAM DATA N

I2S DOWNSTREAM DATA M

I2S DOWNSTREAM DATA M + 1I2S DOWNSTREAM DATA M + 2

I2S UPSTREAM DATA N

I2S UPSTREAM DATA N + 1

I2S UPSTREAM DATA N + 2

I2S DOWNSTREAM DATA M - 2I2S DOWNSTREAM DATA M - 1I2S DOWNSTREAM DATA M

DNSTREAM

A2B DATA

M-1

UPSTREAM

A2B DATA

N-1

DNSTREAM

A2B DATA

UPSTREAM

A2B DATA

DNSTREAM

A2B DATA

M+1

UPSTREAM

A2B DATA

N+1

SUPERFRAME

I2S RX

DATA

I2S TX

DATA

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