CY28341-3
Swing Select Functions Through Hardware
Board Target
Trace/Term Z
Reference R,
IREF = VDD/(3*Rr)
MULTSEL
Output Current
VOH@Z
1
50 Ohm
Rr = 475 1%,
IREF = 2.32mA
IOH = 6* Iref
0.7V@50
Meanwhile, the system BIOS is running its operation with the
new frequency. If this device receives a new SMBus command
to clear the bits originally programmed in the Watchdog timer
bits (reprogram to 0000) before the Watchdog times out, then
this device will keep operating in its normal condition with the
new selected frequency.
Watchdog Self-Recovery Sequence
This feature is designed to allow the system designer to
change frequency while the system is running and reboot the
operation of the system in case of a hang-up due to the
frequency change.
When the system sends an SMBus command requesting a
frequency change through the Dial-a-Frequency Control
Registers, it must have previously sent a command to the
Watchdog timer to select which time-out stamp the Watchdog
must perform, otherwise the System Self-Recovery feature will
not be applicable. Consequently, this device will change
frequency and then the Watchdog timer starts timing.
The Watchdog timer will also be triggered if you program the
software frequency select bits (FSEL) to a new frequency
selection. If the Watchdog times out before the new SMBus
reprograms the Watchdog timer bits to (0000), then this device
send a low system reset pulse, on SRESET# and changes
Watchdog time-out bit to “1”.
W
AT C H D O G T IM ER
PR O G R AM M IN G
R ESET W AT C H D O G T IM ER
Set W D T imer Bits =
C lear W D Alarm bit
0
0
=
IN IT IAL IZ EW AT C H D O G T IM ER
Set F req uency R evert Bit
Set W D T imer Bits
C H AN G E F R EQ B Y
SET SO F T W AR EF SEL
Set SW F req _Sel bits
Set F S override bit
C H AN G E F R EQ B Y SET D IAL -A-
F R EQ U EN C Y
C H AN G E F R EQ B Y
SET D IAL -A-R AT IO
Load
M and N R eg isters
1
Select
a different divider ratio
Set Pro_F req _EN
=
C O U N T D O W N W D T IM ER
Send 3ms R eset Pulse
NO
W
D T im er = 0
C L EAR W D T IM ER
Set W D Alarm
=
1
F req u en cy R ev ert B it =
Set F req uency to
F S_H W_Latched
0
F req u en cy R ev ert B it =
Set F req uency to
F S_SW Setting
1
SR ESET # = 0 fo r 3 m sec
R eset & R ev ert
F req u en cy b ack
Figure 1. Watchdog Self Recovery Sequence Flowchart
Rev 1.0,November 21, 2006
Page 9 of 19
SPECTRALINEAR [ SPECTRALINEAR INC ]
