4DSP FMC150 Manual do utilizador - Página 14

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FMC150 User Manual

5 Controlling the FMC150

Good knowledge of the internal structure and communication protocol of relevant onboard

devices is required for controlling the FMC150. This document only provides guidelines for

programming the devices. For detailed information it is recommended to refer to the

datasheets listed in the related documents section of this document.

Apart from enabling the onboard reference and VCXO the whole clock tree is controlled by

programming the CDCE72010 device through a serial communication bus. The following

guidelines should be taken into account:

1. The internal reference is enabled by driving REF_EN high. The internal reference

should only be enabled in case internal clock is used and there is no external reference

applied.

2. The onboard VCXO is enabled by default, but can be disabled through the GPIO pins

on the AMC7823 (see section 5.4). This may be useful when using external clock.

3. It is recommended to disable the unused clock outputs.

4. It is recommended to disable PLL functions and VXCO input on the CDCE72010 when

an external sampling clock is applied.

5. In case internal clock is used the PLL functions needs to be enabled. The

recommended phase detector frequency is 160kHz. In case the internal reference is

used the reference divider should be set to 625. The VCO divider is set to 4608.

6. Other phase detector frequencies may be used, but stability of the PLL is not

guaranteed in all cases.

Controlling the ADC enables advanced control of the digitizing process. The ADS62P49 can

be programmed through a serial communication interface to change the output format or using

advanced settings among which gain control, offset correction, and several power down

modes.

1) Low speed mode should be selected for sampling frequencies below 80Msps.

2) External reference should never be enabled.

3) Do not enable CMOS mode when there is LVDS termination on the carrier card.

Controlling the DAC enables advanced control of the conversion process. The DAC3283 can

be programmed through a serial communication interface to change the input format or using

advanced settings among which gain control, offset correction, and several power down

modes.

1) The communication bus can only be used in unidirectional mode; thus using SDIO as

data input and ALARM_SDO as data output.

January 2012

FMC150 User Manual

www.4dsp.com

r1.6

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