[ICE DEMO BOARD] Ethercat LED's U29 fet buffer

eugenio

Expert 1505 points

Other Parts Discussed in Thread: TLK110, AM3359

In ICE demo board schematic there is a fet buffer named U29:

What's the purpose of that buffer?

It takes signals from TLK110 (RX_ERR and LINKLED) and feeds them to AM3359 cpu;

Does it isolate SYSBOOT[12:13] signals from TLK110 to get the CPU to sample properly their value at boot time?

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Eugenio,

Yes, that's correct. It isolates the B_PRUETH0... signals from the processor at boot time. FET_nOE is connected to UART1_CTSn pin, which is high-impedance with an active pullup resistor at reset release time in mode 7 (GPIO0_12), so that it would have to be controlled by software in order to enable U29. By the way the correct part number is SN74CB3Q3306APW (this is mentioned in ICE Errata).

0 Rick Brower over 11 years ago in reply to Biser Gatchev-XID

Prodigy 130 points

Ok so what might happen, theoretically, if sysboot[12] was pulled high on startup? All other reserved sysboot pins would be in their proper state. Would the system boot as normal, or is this some type of TI internal use mode? Thanks

0 Biser Gatchev-XID over 11 years ago in reply to Rick Brower

TI__Guru**** 393215 points

The AM335X TRM Rev. J states in Table 26-7 that SYSBOOT[12] must be low for this boot setting. This is required for proper booting.

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[ICE DEMO BOARD] Ethercat LED's U29 fet buffer