I'd like to design a system based on the AM4372 SOC.
I'd like the GPMC bus to be clocked with an external oscillator that has a frequency of 43.75 MHz.
Does this device support that ?
Hi.
What I'd like to know is whether the GPMC clocked by an external clock pin at 43.75MHz
Hi Shai,
Short answer is no the GPMC cannot take in an external clock source as its reference clock. Its only clock source comes through the core PLL and HSDIVIDER. OSC0 is limited to 19.2-MHz, 24-MHz, 25-MHz, or 26-MHz. The PLL could be bypassed, but core will run very slowly (more for low power modes).
The only clock source available to the GPMC_FCLK is pd_per_l3s_gclk which equals CORE_CLKOUTM4 / 2. This clock is typically 100MHz, but configurable by adjusting HSDIVIDER M4 divider. Note that multiple other peripherals also derive their clocks from this output clock and you may break their functionality by adjusting it!
Additionally, the GPMC_CLK pin is an output only from the processor. You cannot use an external input.
Refer to TRM Table 9-3. GPMC Clock Signals
and TRM Figure 6-14. Core PLL Structure
TRM link: https://www.ti.com/lit/pdf/SPRUHL7
You can also dive into the clocks of AM437x using the Clock Tree Tool
- See https://www.ti.com/tool/CLOCKTREETOOL
- download CLOCKTREETOOL-SITARA
- Requires Java Runtime Engine such as JDK v202 (last free version)
- Once installed, run CTT-Sitara-Legacy.jar
Hope this helps,
Mark
