DM385, DM388
SPRS821D –MARCH 2013–REVISED DECEMBER 2013
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The differential clock source is required to meet the REFCLK AC Specifications outlined in the PCI
EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 2.0, at the input to the AC coupling
capacitors.
In addition, LVDS clock sources that are compliant to the above specification, but with the following
exceptions, are also acceptable:
Table 7-13. Acceptable Exceptions to the REFCLK AC Specifications for LVDS Clock Sources
PARAMETER
Differential High-Level Input Voltage
Differential Low-Level Input Voltage
MIN
125
MAX
1000
-125
UNIT
mV
VIH
VIL
-1000
mV
7.4.3 CLKIN32 Input Clock
An external 32768-Hz clock input can optionally be provided at the CLKIN32 pin to serve as a reference
clock in place of the RTCDIVIDER clock for the following Modules:
•
•
•
•
•
RTC
GPIO0/1/2/3
TIMER1/2/3/4/5/6/7
ARM Cortex-A8
SYNCTIMER
The CLKIN32 source must meet the timing requirements shown in Table 7-16.
7.4.4 Output Clocks Select Logic
The device includes two selectable general-purpose clock outputs (CLKOUT0 and CLKOUT1). The source
for these output clocks is controlled by the CLKOUT_MUX register in the Control Module (see Figure 7-
12).
150
Power, Reset, Clocking, and Interrupts
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