CY28RS400ZCT SPECTRALINEAR [SpectraLinear Inc], CY28RS400ZCT Datasheet - Page 11

• Manufacturer Part Number: CY28RS400ZCT
• Description: Clock Generator for ATI RS400 Chipset
• Manufacturer: SPECTRALINEAR [SpectraLinear Inc]

Rev 1.0, November 22, 2006
CLK_REQ[0:1]# Description
The CLKREQ#[1:0] signals are active low input used for clean
stopping and starting selected SRC outputs. The outputs
controlled by CLKREQ#[1:0] are determined by the settings in
register bytes 4 and 5. The CLKREQ# signal is a de-bounced
signal in that it’s state must remain unchanged during two
consecutive rising edges of DIFC to be recognized as a valid
assertion or de-assertion. (The assertion and de-assertion of
this signal is absolutely asynchronous).
CLK_REQ[0:1]# De-assertion [Low to High transition]
The impact of deasserting the CLKREQ#[1:0] pins is all DIF
outputs that are set in the control registers to stoppable via
de-assertion of CLKREQ#[1:0] are to be stopped after their
next transition. When the control register CLKREQ# drive
mode bit is programmed to ‘0’, the final state of all stopped
CPUC(Free Running
CPUT(Free Running
CPUC(Stoppable)
CPUT(Stoppable)
CPUC(Free Running)
CPUT(Free Running)
CPU_STOP#
CPUC(Stoppable)
CPUT(Stoppable)
SRCC(free running)
SRCT(free running)
CPU_STOP#
SRCT(stoppable)
SRCT(stoppable)
CLKREQ#X
PD
PD
Figure 9. CLK_REQ#[0:1] Assertion/Deassertion Waveform
Figure 7. CPU_STP#= Driven, CPU_PD = Driven
Figure 8. CPU_STP# = Hi-Z, CPU_PD = Hi-Z
SRC signals is SRCT clock = High and SRCC = Low. There is
to be no change to the output drive current values, SRCT will
be driven high with a current value equal 6 x Iref,. When the
control register CLKREQ# drive mode bit is programmed to
‘1’, the final state of all stopped DIF signals is low, both SRCT
clock and SRCC clock outputs will not be driven.
CLK_REQ[0:1]# Assertion [High to Low transition]
All differential outputs that were stopped are to resume normal
operation in a glitch free manner. The maximum latency from
the assertion to active outputs is between two–six SRC clock
periods (two clocks are shown) with all SRC outputs resuming
simultaneously. If the CLKREQ#
programmed to ‘1’ (three-state), the all stopped SRC outputs
must be driven high within 10 ns of CLKREQ#[1:0] assertion
to a voltage greater than 200 mV.
CY28RS400
1.8mS
drive mode bit is
1.8mS
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