GS2985 datasheet(34/45 Pages) SEMTECH

34 / 45 page

GS2985 Multi-Rate SDI Reclocker with Equalization &

De-emphasis

Data Sheet

36663 - 5

July 2012

34 of 45

Proprietary & Confidential

4.15.11 Writing to a Single Device in the Chain

The following example shows how to write to a single device in a chain:

Figure 4-14: Daisy Chain Write to a Single Device

1. The command is issued to Chain Position N.

2. 32xN cycles are required to shift the command through N devices. The device at chain

position N executes the command.

3. 32 additional cycles are required to complete the communication.

4.15.12 Reading from all Devices

To read from all devices in the chain, a Read command is issued for each device consecutively.

After each command, the data is held HIGH for 16 cycles. Once a device recognizes it is being

talked to, it will output data from the register requested. Clock needs to be applied to cycle the

output data through all devices in the chain.

Figure 4-15: Daisy Chain Read

1. Read command is issued to the last device in the chain, followed by Read commands to the

lower chain positions.

2. Clock is applied to cycle the output data through the chain.

DataN [15:0]

MOSI CommandN [15:0]

Data High 32xN cycles

Data High 32 cycles

Chain Position = N

Chain Position = N (N = 0 for first device in chain)

DataN [15:0]

CommandN’ [15:0]

MISO

Command 2

Command 1

SDI

SDO

Data HIGH for

16 cycles

Command 0

Data HIGH for

16 cycles

Data HIGH for

16 cycles

(Chain Position = 0)

Data2

Data0

Data1

Data held

HIGH for 32x3

cycles

Command2’

Command1’

Command0’

SDI

SDO

(Chain Position = 1)

(Chain Position = 2)

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