STC3800 Datasheet, PDF (34/48 Pages) Connor-Winfield Corporation – INTEGRATED - STRATUM 3E TIMING SOURCE

Application Notes continued
Master/Slave Operation and Control – The Master/Slave state is always manually controlled by the application.
Master or slave state of a device is determined by the M/S pin. Choosing the master/slave states is a function of the
application, based on the configuration of the rest of the system and potential detected fault conditions.
When operating in Hardware Control or Register Access Manual Control mode, it is important to set the slave reference
selection the same as the master to ensure use of the same reference when/if the slave becomes master. In Register
Access Manual Control mode, the Ref_Mask register should also be written to the same value for both devices.
Master/slave switches should be performed with minimal delay between switching the states of each of the two devices.
This can be easily accomplished, for example, by controlling the master/slave state with a single signal, coupled to one
of the devices through an inverter.
In the case of Register Access Automatic Control mode, where reference selection is automatic, it is necessary to read
the operational mode (bits 3-0) from the master’s Op_Mode register and write it to the slave’s Op_Mode register. The
master’s reference selection will then be used by the slave when it becomes master. In addition to having the
references populated
the same, and in the same order for both devices, it is desirable to write the reference frequency and priority registers
Ref(1-8)_Frq_Priority and the Ref_Mask registers to the same values for both devices to ensure seamless master/
slave switches.
Reset – Device reset is an initialization time function, which resets internal logic and register values. A reset is
performed automatically when the device is powered up. Registers return to their default values, as noted in the register
descriptions. Device mode and functionality following a reset are determined by the state of the various hardware
control pins.
Preliminary Data Sheet #: TM061 Page 34 of 48 Rev: P06 Date: 11/22/04
© Copyright 2001 The Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice