Clock; Figure 4-5. Oscillator Clock Tree; Figure 4-6. Crystal Clock Tree; Table 4-2. Clock Source - Texas Instruments AM263 Series User Manual

Hardware Description

4.4 Clock

The AM263x SoC requires a 25-MHz clock input for XTAL_XI. All reference clocks required for the SoC and the
three Ethernet PHY's are generated from a single four output clock buffer (LMK1C1104PWR), which is sourced
from a single 25-MHz LVCMOS Oscillator by default. A clock buffer is used for level translation from 3.3 V to 1.8
V.
The Control Card also requires a 16-MHz clock source for the TM4C129 microcontroller for UART-USB JTAG
support.
Alternatively, the SoC clock input can be sourced from a single 25-MHz crystal. To use the crystal there must
be resistors mounted and unmounted. When the Crystal is used as a clock source then the AM263x CLKOUT0
signal is used to source the four output clock buffer for the Ethernet PHY reference clock signals.
The following table describes the proper resistors to be mounted and DNI'd in order for each clock source
configuration.
Clock Source
25-MHz LVCMOS Oscillator (default)
25-MHz Crystal
20 AM263x Control Card Hardware User's Guide

Figure 4-5. Oscillator Clock Tree

Figure 4-6. Crystal Clock Tree

Table 4-2. Clock Source

Mounted
R161, R135
R158, R155, R134
Copyright © 2023 Texas Instruments Incorporated
DNI
R158, R155, R134
R161, R135
SPRUJ09C – MARCH 2022 – REVISED FEBRUARY 2023
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