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#1 2016-May-20 08:29:32

alice_warp
Member
From: Italy
Registered: 2015-Sep-08
Posts: 53

Clock Rate SPI AD9963

The maximum clock rate of AD9963 SPI is specified in the datasheet:

SERIAL PERIPHERAL INTERFACE
Maximum Clock Rate 50 MHz

What is the real Clock Rate SPI in the Reference Design 802.11 Release v1.3? Is 5 MHz? If yes, what is the reason?

Thanks,
Alice

Last edited by alice_warp (2016-May-20 08:54:51)

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#2 2016-May-20 10:09:16

murphpo
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From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: Clock Rate SPI AD9963

The AD9963 SPI interfaces are tied to the w3_ad_controller core. This core is attached to an AXI interconnect. The core generates the SPI clock by dividing down the AXI interface clock. In the 802.11 ref design the core's AXI interface clock is 160MHz. The SPI clock divider is configured from software (the second argument to ad_init()). The clkDiv argument acts as a bit select into a counter that runs at the AXI interface clock (0: clk/2, 1: clk/4, etc), so AXI_clk = 160MHz and clkDiv=3 should result in a 10MHz SPI clock.

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#3 2016-May-20 11:16:51

alice_warp
Member
From: Italy
Registered: 2015-Sep-08
Posts: 53

Re: Clock Rate SPI AD9963

murphpo wrote:

The AD9963 SPI interfaces are tied to the w3_ad_controller core. This core is attached to an AXI interconnect. The core generates the SPI clock by dividing down the AXI interface clock. In the 802.11 ref design the core's AXI interface clock is 160MHz. The SPI clock divider is configured from software (the second argument to ad_init()). The clkDiv argument acts as a bit select into a counter that runs at the AXI interface clock (0: clk/2, 1: clk/4, etc), so AXI_clk = 160MHz and clkDiv=3 should result in a 10MHz SPI clock.

Thank you. So, I can put any value, but until 40 MHz, right?
I don't want break anything..

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#4 2016-May-20 15:03:39

murphpo
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From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: Clock Rate SPI AD9963

You can try setting clkDiv do 2 or 1; this should give an SPI clock of 20 or 40 MHz.

Out of curiosity, why are you trying to increase the AD9963 SPI clock frequency? The ad_controller only uses this SPI interface during initialization or when changing ADC/DAC settings (adjusting clock dividers, etc). Increasing the SPI clock frequency won't have any affect on the operation of the ADCs/DACs.

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#5 2016-May-23 02:47:23

alice_warp
Member
From: Italy
Registered: 2015-Sep-08
Posts: 53

Re: Clock Rate SPI AD9963

I'm trying to implement something of dynamic, so I need to change ADC/DAC settings in a fast way.
Thank you!

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