2317 Rev 1.1 (17NOV04)
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4.4 Clock Select Control
AES2501A can support a variety of clock sources, ranging in frequency
from 6MHz up through 48MHz. The AES2501A uses a single pin
crystal/resonator oscillator circuit that can also be overdriven with an
external clock source. Clock frequency selection [including clocks driven
into the SYS_CLK pin] is done via the CLKSEL[2:0] input pins. The
following table shows the CLKSEL[2:0] pin configurations:
CLKSEL2
Pin B1
CLKSEL1
Pin B6
CLKSEL0
Pin C5
Crystal/Resonator or Clock
Frequency
0
0
0
6 MHz
0 0
1
Reserved
0
1
0
12 MHz
0 1
1
18
MHz
1 0
0
24
MHz
1 0
1
Reserved
1 1
0
Reserved
1
1
1
48 MHz (PLL Bypass, clock only)
Table 4-1
CLKSEL[2:0] Decode
For USB applications, Crystal/Resonator frequency options include 6, 12, 18, and
24MHz.
4.4.1 Clock
Specification
For the AES2501A, there are several different clocking options available:
Crystal connection, ceramic resonator connection, and external clock
driven. Appropriate application of clock sources is driven the desired
circuit application (interface type) and reference design. This section
addresses the specification requirements for an externally driven clock.
All electrical and environmental conditions from the device specification
apply as well.