GS2985 Datasheet, PDF (34/45 Pages) Gennum Corporation – Uses standard 27MHz crystal

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:
CS
MOSI ^{CommandN [15:0]}
Chain Position = N
DataN [15:0]
MISO
Data High 32xN cycles
Data High 32 cycles
CommandN’ [15:0] DataN [15:0]
Chain Position = N (N = 0 for first device in 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.
CS
SDI
SDO
Command 2
(Chain Position = 2)
Data HIGH for
16 cycles
Command 1
(Chain Position = 1)
Data HIGH for
16 cycles
Command 0
(Chain Position = 0)
Data HIGH for
16 cycles
CS
SDI
Data held
HIGH for 32x3
cycles
SDO Command2’
Data2
Command1’
Data1
Command0’
Data0
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.
GS2985 Multi-Rate SDI Reclocker with Equalization &
De-emphasis
Data Sheet
36663 - 5
July 2012
34 of 45
Proprietary & Confidential