| *:* Jive * Guest Bienvenido, /Invitado/ * Iniciar sesin * Registro * * * * * Inicio Actividad0 Comunicaciones Acciones0 Buscar Ms o Contenido o Personas o Lugares o Marcadores Buscar:Search Advanced Search Analog Devices Worldwide Technical Support EngineerZone Todos los lugares Direct Digital Synthesis (DDS) Discusiones Ingrese un ttulo. No puede publicar un mensaje en blanco. Ingrese su mensaje y vuelva a intentar. *11 Respuestas* Respuesta ms reciente : 24/02/2011 09:27 PM por Radarsign RSS AD9958 non-documented startup issue Esta pregunta es una *supuesta respuesta.* Radarsign Member *Radarsign * 2/12/2010 08:22 AM Actualmente moderados A AD9958 is being used as a quadrature generator for radar testing. None of the modulation capabilities of this part are being used. The part did produce very nice sine waves but a recent code change caused the output to disappear. A SPI logic probe verified that the device was receiving the proper initialization code, same code as when the part produced an output. Register values are below.freqh = $0040 freql = $0fb9 ' 33.333Mhz for 32583hz output defaultphase = $0000 CSR = $c2 ' FR1a = $00 ' FR1b = $0000 FR2 = $0040 CFRa = $00 CFRb = $0201 ACRa = $00 ACRb = $13FF' phase in MSB 14 bits ch0=$42, ch1=$82, both=$c2 temp set so PLL is off' $0300=200mV, $0200=50mV, SINE ' Max amplitudeA 5us positive going pulse on IO_UPDATE at the completion of the register data load sends the values to the core.We went back to the code change and discovered that we had terminated SYNC_IO ((SDIO_3) low as we were in 2 bit serial comm mode and we did not need to terminate a serial command early. This should be the proper termination for this pin in such cases but this was the cause of the output not being updated. See page 31, left column, paragraph 6 of the data sheet.Examining the prior working code we observed that SDIO_3 was high during the 5ms reset pulse and when brought low after the reset but before the DDS' chip select was brought low. This enables the proper output signal to be generated but is not in the documentation. Terminating SDIO_3 high or low causes the output to not function. It seems to need to be high and then go low to enable proper operation.What is the proper sequence of signals to properly bring up the device with SDIO_3, Master Reset, and IO_UPDATE? None of the timing diagrams in the data sheet seem to show this requirement of SYNC_IO needing to have a high to low transition.A schematic is attached.Charles Jenkins Radarsign * HTX TEST Quadrature Gen D.pdf (279.1 K) * 3671 Vistas * Etiquetas: ninguno (agregar ) quadrature , dds , ad9958 , sync_io * *1. Re: AD9958 non-documented startup issue * Georgy Regular Contributor *Georgy * 2/12/2010 11:23 AM (en respuesta a Radarsign ) Actualmente moderados Hi, Radarsign! I hope only one CLK used with? (There are two CLKs = 20 MHz and 33,333 MHz)/ And R208 (A...D) resistance? Not large? This ones may be in the way programing. o Reportar abuso o Me gusta (0 ) * *2. Re: AD9958 non-documented startup issue * Radarsign Member *Radarsign * 2/12/2010 03:06 PM (en respuesta a Georgy ) Actualmente moderados Hello GeorgyThank you for your insight. The two clocks are options. Of course only one at a time :-). R208 is 10K and is just for unknown options if needed. Easier to overdrive a resistor than cut a trace. Since the IO functions of these pins are not programmed their termination should not matter.As far as programming is concerned the same code was used to produce a sine wave or produce a zero output (no current sinks operating DC level on output is 1.8V). The only difference is in how I manipulated the SDIO_3 while in 2 wire mode. In this mode SDIO_3 issupposed to be used to stop a register load at some time before the end if brought high so I figured terminating it low was best if that function is not needed. Termination low means no putput. Same with termination high. Only if it transitions high to low does the output function. This is what I am curious about. No info on this in the data sheet.From: Georgy Shebetovskiy analog@sgaur.hosted.jivesoftware.com Sent: Thursday, December 02, 2010 11:23 AM To: Charles Jenkins Subject: Re: AD9958 non-documented startup issue New message: "AD9958 non-documented startup issue" Re: AD9958 non-documented startup issue Analog Devices EngineerZoneAD9958 non-documented startup issuereply from Georgy Shebetovskiy in Direct Digital Synthesis (DDS) - View the full discussion