22-10-2016, 12:56 PM
(This post was last modified: 22-10-2016, 12:58 PM by ppppenguin.)
I remember the ZNA134 and also the ZNA234. I still have a few lurking. The Philips SAA1043 and the later SAA1101 are rather better SPG chips. I have used all of them in the past.
Rather better than any of these is if you have any form of reasonably modern programmable logic device available. Here's the VHDL I used at the Vintage Wireless Museum to generate a few test patterns. This was an afterthought added on to the controller for the audio/video router that's the heart of the Museum's TV distribution system.
This used a low cost module that contains a Xilinx Coolrunner CPLD. Many modules are available that contain devices by Xilinx, Altera, Lattice, possibly others too. The VHDL etc tools are usually freely available online. The VHDL I wrote would synthsise equally well on an Altera or lattice device. I built a very crude DAC with 4 resistors to make the video output. See contents of patgen.zip
The original need was for a full screen (or at leat a lot of peak white) peak white so that RF level measurements could be made sensibly on System A. You need a decent area of 100% carrier for a test set to work.
As an experiment I later managed to get the device to make PAL colour bars. Obviously an 8 bit DAC was needed so I did a simple R/2R ladder. With some difficulty I managed to shoehorn in a PAL generator. I think I wrote this up elsewhere on GVR. the design needed at least one multiplier and a sine table. The multiplier was a tricky thing to shoehorn into a small device. Automated synthesis gave horrible results. Needed a lot of craft skill to make a design that was both compact and workable. I think the ZIP file contains the final working design. Never actually installed it at the Museum as it was purely an exercise to see if it was feasible. See contents of colourbar.zip
If I was serious about a compact universal pattern generator I'd use a small CPLD (a small CPU like Frank's might also work) to address a flash memory. DAC also needed, either a R-2R ladder or a fairly fast chip. SD cards are as cheap as chips and will hold loads of patterns as literal data. Moving picture sequences possible too. If you want PAL colour then simply store all 8 fields of the sequence. All the real work is then on a PC, generating the data to program into the SD card. None of this is new, Richard Russell did it years ago for his testcard generator. The difference now is that flash memory is large and cheap.
Rather better than any of these is if you have any form of reasonably modern programmable logic device available. Here's the VHDL I used at the Vintage Wireless Museum to generate a few test patterns. This was an afterthought added on to the controller for the audio/video router that's the heart of the Museum's TV distribution system.
This used a low cost module that contains a Xilinx Coolrunner CPLD. Many modules are available that contain devices by Xilinx, Altera, Lattice, possibly others too. The VHDL etc tools are usually freely available online. The VHDL I wrote would synthsise equally well on an Altera or lattice device. I built a very crude DAC with 4 resistors to make the video output. See contents of patgen.zip
The original need was for a full screen (or at leat a lot of peak white) peak white so that RF level measurements could be made sensibly on System A. You need a decent area of 100% carrier for a test set to work.
As an experiment I later managed to get the device to make PAL colour bars. Obviously an 8 bit DAC was needed so I did a simple R/2R ladder. With some difficulty I managed to shoehorn in a PAL generator. I think I wrote this up elsewhere on GVR. the design needed at least one multiplier and a sine table. The multiplier was a tricky thing to shoehorn into a small device. Automated synthesis gave horrible results. Needed a lot of craft skill to make a design that was both compact and workable. I think the ZIP file contains the final working design. Never actually installed it at the Museum as it was purely an exercise to see if it was feasible. See contents of colourbar.zip
If I was serious about a compact universal pattern generator I'd use a small CPLD (a small CPU like Frank's might also work) to address a flash memory. DAC also needed, either a R-2R ladder or a fairly fast chip. SD cards are as cheap as chips and will hold loads of patterns as literal data. Moving picture sequences possible too. If you want PAL colour then simply store all 8 fields of the sequence. All the real work is then on a PC, generating the data to program into the SD card. None of this is new, Richard Russell did it years ago for his testcard generator. The difference now is that flash memory is large and cheap.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
