GS2965 Datasheet, PDF (30/41 Pages) Gennum Corporation – Uses standard 27MHz crystal

4.15.9 Read & Write Operation - Daisy Chained Devices
In a serial daisy chain configuration, Read and/or Write operations can be performed to
multiple devices in the chain via consecutive operations. Figure 4-12 below shows a
simple 3 device configuration.
MISO
MOSI
µC
SDI SDO
GS2965
SDI SDO
GS2965
SDI SDO
GS2965
Figure 4-12: Three Devices in Daisy Chain Configuration
4.15.10 Writing to all Devices
When writing to all devices in the chain, a Write Command and corresponding Data is
required for each device. When the devices are being configured in the same way, all of
them will have the same command and data with the exception of the Chain Position
bits. This example assumes a 3-device daisy chain. A command is issued to the last
device in the chain first, although it is possible to talk to the devices in any order.
CS
MOSI ^{Command2 [15:0]}
Chain Position = 2
Data [15:0]
Command1 [15:0]
Chain Position = 1
Data [15:0]
Command0 [15:0]
Chain Position = 0
Data [15:0]
Data High 32 cycles
MISO
Command0' [15:0]
Data [15:0]
Figure 4-13: Daisy Chain Write
1. The first command issued in time is the command for the last device in the chain
(chain position = 2). When the first device receives this command it will recognize
that the Chain Position is 2 and will not execute the command. It will duplicate the
command and data word at its output and decrement the Chain Position by one.
2. Consecutive commands are issued for each device in the chain as shown.
GS2965 Multi-Rate SDI Reclocker with Equalization &
De-emphasis
Data Sheet
52462 - 4
July 2012
30 of 41
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