8 bit parallel mode

Designing hardware and software that uses the VS23S0X0 family of ICs as a 8-bit or SPI SRAM memory or as a Video Controller for generating Composite Video (TV-Out) or driving other kinds of displays.
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ricortes
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8 bit parallel mode

Post by ricortes » Wed 2019-03-06 6:08

The guide & datasheet specify:
"initialization and enabling of the Video Display Controller are made by SPI so during that period
8-bit parallel interface can’t be used."

Does this mean if you plan on using the video function, you must implement SPI as a minimum to set up the screen even if you plan on using the 8 bit parallel mode for everything else?

Hannu
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Re: 8 bit parallel mode

Post by Hannu » Wed 2019-03-06 13:54

Yes. 8-bit parallel interface can access only memory. With SPI you can access memory and all the registers of the VS23S0x0 ICs.

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Panu
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Re: 8 bit parallel mode

Post by Panu » Thu 2019-03-07 20:24

That's true. And as the 8 bit data pins are shared with SPI, you effectively need to bit bang the SPI writes to set up the video controller registers and then you can use the 8 bit data bus for updating the video memory in real time.

Quad bit SPI is good mode too, if your MCU handles it with hardware. It's fast enough for full screen video.
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JimDrew
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Re: 8 bit parallel mode

Post by JimDrew » Mon 2019-03-11 8:57

I am using a dsPIC33 interfaced the VS23S010-D. With this chip you might notice that some of the parallel lines are also part of the SPI lines. For the dsPIC33 I am able to remap pins so I don't have to bit-bang the SPI. I just change what the pin use is for and the hardware SPI of the chip works fine for setup. I use DMA on the parallel port to move the data to the VS23S010-D's bus so I literally only have the overhead of filling the dsPIC33's memory with whatever I want going to the VS23S010-D's display buffer.

ricortes
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Re: 8 bit parallel mode

Post by ricortes » Mon 2019-03-11 21:32

Thanks for the input! I have multiple systems I would like to try the VS23S with but one of the systems will have to be bit banging a SPI from a PIA. I will take a look at the Quad bit SPI to see if it will eliminate the need for parallel I/O. The parallel I/O would not be difficult to implement since I already have open spots in the memory map with decoded !CS available. I have the parts on order for 5V to 3.3V level memory mapped device but I flip flop on the speed of 8 bit parallel transfers vs. the simplicity of a bit banged SPI and just sticking with it.

JimDrew
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Re: 8 bit parallel mode

Post by JimDrew » Tue 2019-03-12 0:43

The SPI clock speed is limited compared to what the parallel lines will handle. So, I guess it depends on what CPU you are interfacing to the VS23S010-D. For me, I wanted the fastest method and SPI (even QSPI) was not the way to go.

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