AM3352: GPMC to HPI connection issue

yimin bai1

Expert 1495 points

Part Number: AM3352

Hi Sir

we connect GPMC intetface of AM3352 with HPI interface of C6748 and implement the SW code.

we also set internal pullup for AM3352 WAIT0 and DSP6748 UHPI_HRDY

there is one issue about the pullup resisor of GMPC wait0 pin.

If wait0 pullup resisor is 33ohm , the communication is succeed.

If wait0 pullup resisor is 4.7kohm , the communication is failed.

what is the suitable pull resistor value and what is the GPMC wait0 input impedence of AM3352 ?

thanks for reply

Yimin

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

Do you mean that you have both external pullup and internal pullup on WAIT0?

0 yimin bai1 over 9 years ago in reply to Biser Gatchev-XID

Expert 1495 points

Hi Sir

what is your suggestion ?

Should we remove external pullup and enable internal pullup on WAIT0 ?

BR
Yimin

0 Biser Gatchev-XID over 9 years ago in reply to yimin bai1

TI__Guru**** 393215 points

If you have both external pullup and internal pullup on WAIT0, they are connected in parallel. Besides this external value of 33 Ohms may damage the DSP6748 UHPI_HRDY output. Please check if UHPI_HRDY is push-pull or open-drain output and what current can it sink/source.

0 yimin bai1 over 9 years ago in reply to Biser Gatchev-XID

Expert 1495 points

Hi Sir

thanks for reply.

Do we need external pullup on WAIT0 or just need to enable internal pullup on WAIT0 would be enough.

thanks for reply.

0 Biser Gatchev-XID over 9 years ago in reply to yimin bai1

TI__Guru**** 393215 points

The AM335X WAIT0 input does not require any pullup. Whether you need a pullup and what value depends on the DSP output from the other side, and I cannot comment about that, as DSP's are not supported on this forum. Looking at the wiki: processors.wiki.ti.com/.../AM335x_GPMC_to_OMAP-L13x_HPI_Interface no pullups are used there.

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AM3352: GPMC to HPI connection issue