X

8

Q

© 2010 Exar Corporation

21/27

Rev. 1.0.3

When powering in sync mode the slave unit will initially power up with its internal clock to transfer

the configuration memory. Once this transfer occurs, then the unit is set to function as a slave unit.

In turn the unit will take the external clock provided by the master to run as its main internal clock.

GPIO2

GPIO2

XRP7708

configured

as a master

XRP7708

configured

as a slave

CLK_OUT

SYNC_OUT

SYNC_IN

CLK_IN

GPIO1

GPIO1

Fig. 23: Master/Slave Configuration of the XRP7708

External Clock Synchronization Master Slave combination

When an external clock is used, the user will need to setup the master to also have an external

clock in function. All of the same rules apply as in the External clock synchronization, Synchronized

operation as a Slave unit section of this document. There are two ways of synchronizing this,

either the external clock going to both Master/Slave CLK_IN, or CLK_IN can go to the Master, and

the Master can synchronize SYNC_OUT and CLK_OUT to the Slave.

GPIO2

GPIO2

XRP7708

Configured as a

master with

external clock sync

XRP7708

configured

as slave

SYNC_OUT

SYNC_IN

CLK_IN

CLK_IN

GPIO1

GPIO1

Fig. 24: External Clock Synchronization Master Slave Combination

GPIO2

GPIO2

XRP7708

Configured as a

master with

external clock sync

XRP7708

configured

as slave

SYNC_OUT

SYNC_IN

CLK_IN

CLK_IN

GPIO1

GPIO3

CLK_OUT

GPIO1

Fig. 25:Alternative External clock synchronization Master Slave combination