[FAQ] AM623: How to set spread spectrum for AM623?

Neil Lai

Part Number: AM623

Tool/software:

Hi Expert,

Our product needs to pass EMC RE test. We referred the thread, https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1384055/am623-lcd_pclk-setting-and-emc-re-issues-for-dpi-interface-of-am62x-dss, and we find this speard spectrum can helpl us to improve the test result. We also know AM623 does not support clock spread spectrum function now. But we still want to know how to set spread spectrum function for PLL16 as default. Thanks.Below are the commands we use to do spread spectrum.

./devmem2 0x690020 w 0x18013
sleep 3
./devmem2 0x690040 w 0x8000
sleep 3
./devmem2 0x690040 w 0x0
./devmem2 0x690044 w 0x6000A

best regards,
Neil

over 1 year ago

0 peaves over 1 year ago

TI__Guru 63145 points

This topic has already been discussed on multiple AM62x E2E threads.

(+) AM6422: spread spectrum clocking: restrictions when using UHS-I SD Cards - Processors forum - Processors - TI E2E support forums

(+) AM2432: AM2432 Spread Spectrum Modulation setting - Processors forum - Processors - TI E2E support forums

(+) AM620-Q1: Does eMMC support SSC? - Processors forum - Processors - TI E2E support forums

Currently SSC is not supported on AM62x devices, but there is a plan to support it in the future on the parallel video output port (DSS0). The device does not support it on any other peripheral.

(+) AM625: external and internal spread spectrum oscillator support - Processors forum - Processors - TI E2E support forums

1) Yes. You can use a 1.8V LVCMOS clock source rather than a crystal circuit. However, the current datasheet does not define the MCU_OSC0 LVCMOS Digital Clock Source Requirements. We will be adding these requirements to the next revision of the datasheet. For now, please refer to the "MCU_OSC0 LVCMOS Digital Clock Source" section of the AM62Dx or AM62Px datasheets. The requirements for AM62x will be the same.

2) An external 1.8V LVCMOS source is supported, but not a Spread Spectrum source. As mentioned above, please follow the requirements defined in the "MCU_OSC0 LVCMOS Digital Clock Source" section of the AM62Dx or AM62Px datasheets.

3) That is correct. SSC is not currently supported on AM62x. We may support SSC on the PLL that sources the DSS peripheral in the future, but there are no plans to support SSC for any other PLLs.

(10) AM625: How to use PLL Spread Spectrum Modulation Module in AM625 - Processors forum - Processors - TI E2E support forums

(10) AM625: Is spread spectrum functionality supported in AM625 ? - Processors forum - Processors - TI E2E support forums

(10) AM625: PLL Spread Spectrum Modulation - Processors forum - Processors - TI E2E support forums

Regards,
Paul