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Observer jblock
Observer
212 Views
Registered: ‎10-30-2014

Zynq 7000 SPI Master Command Sequence in UG585

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The example "Master Mode Data Transfer" appears to have the order swapped for the controller enable and the Chip Select (UG585 17.3.3 steps 3 & 4). If the Clk line does not have a pull-up (as is typically the case) the clock may drift low becasue the MIO Clk pin is a tri-state pin. This causes an erroneous rising Clk edge to the slave when enabled. The scope screenshot below represents this command sequence. The green is the clock (which has drifted low) and the yellow is the Chip Select. The result is the interface does not function correctly. If the controller is enabled first, the Clk is driven (and correctly high) when Chip Select is asserted so there is no "extra" rising edge and the interface works properly. Does the UG assume there is an external pull-up on Clk (not mentioned anywhere) or is the sequence incorrect?

The setup used was the most simple case. SPI on MIO, single slave, no other masters, slave is Mode 3.

ug585.jpg

Prod_I2C_Debug1.jpg

1 Solution

Accepted Solutions
Moderator
Moderator
105 Views
Registered: ‎07-31-2012

Re: Zynq 7000 SPI Master Command Sequence in UG585

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Hi @jblock ,

Step 3 and 4 are swapped.

Controller should be enabled followed by slave selection.

Regards

Praveen


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3 Replies
Moderator
Moderator
152 Views
Registered: ‎07-31-2012

Re: Zynq 7000 SPI Master Command Sequence in UG585

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Hi @jblock ,

We recommend the pull-up for SPI in XMP277 schematic checklist not in user guide.

PS_SPI_pull-up.jpgZynq-7000 PS SPI pull up recommendation

Regards

Praveen


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Observer jblock
Observer
140 Views
Registered: ‎10-30-2014

Re: Zynq 7000 SPI Master Command Sequence in UG585

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Hello Praveen,

The problem is the clock and it is the one signal where a pull-up is not recommended.

Thanks

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Moderator
Moderator
106 Views
Registered: ‎07-31-2012

Re: Zynq 7000 SPI Master Command Sequence in UG585

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Hi @jblock ,

Step 3 and 4 are swapped.

Controller should be enabled followed by slave selection.

Regards

Praveen


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Don’t forget to reply, kudo, and accept as solution.
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