T MS 3 20 VC 54 02
F IX EDĆPO I NT DI GI TAL SI G NAL P RO C ES S O R
SPRS079E – OCTOBER 1998 – REVISED AUGUST 2000
divide-by-two clock option (PLL disabled)
The frequency of the reference clock provided at the X2/CLKIN pin can be divided by a factor of two to generate
the internal machine cycle. The selection of the clock mode is described in the clock generator section.
When an external clock source is used, the frequency injected must conform to specifications listed in the timing
requirements table.
NOTE:All revisions of the ’5402 can be operated with an external clock source, provided that the proper
voltage levels be driven on the X2/CLKIN pin. It should be noted that the X2/CLKIN pin is referenced to
the device 1.8V power supply (CVdd), rather than the 3V I/O supply (DVdd). Refer to the recommended
operating conditions section of this document for the allowable voltage levels of the X2/CLKIN pin.
timing requirements (see Figure 11)
MIN
MAX
UNIT
ns
†
t
t
t
Cycle time, X2/CLKIN
Fall time, X2/CLKIN
Rise time, X2/CLKIN
20
c(CI)
f(CI)
r(CI)
8
8
ns
ns
†
This device utilizes a fully static design and therefore can operate with t
approaching 0 Hz.
approaching ∞. The device is characterized at frequencies
c(CI)
†
switching characteristics over recommended operating conditions [H = 0.5t
Figure 11, and the recommended operating conditions table)
] (see Figure 10,
c(CO)
PARAMETER
MIN
TYP
MAX
UNIT
ns
‡
10
†
t
Cycle time, CLKOUT
2t
c(CI)
10
c(CO)
t
Delay time, X2/CLKIN high to CLKOUT high/low
Fall time, CLKOUT
4
17
ns
d(CIH-CO)
t
2
2
ns
f(CO)
t
t
t
Rise time, CLKOUT
ns
r(CO)
Pulse duration, CLKOUT low
Pulse duration, CLKOUT high
H–2
H–2
H
H
ns
w(COL)
w(COH)
ns
†
This device utilizes a fully static design and therefore can operate with t
approaching 0 Hz.
It is recommended that the PLL clocking option be used for maximum frequency operation.
approaching ∞. The device is characterized at frequencies
c(CI)
‡
t
r(CI)
t
f(CI)
t
c(CI)
X2/CLKIN
CLKOUT
t
w(COH)
t
f(CO)
t
c(CO)
t
r(CO)
t
d(CIH-CO)
t
w(COL)
Figure 11. External Divide-by-Two Clock Timing
37
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