>> now on The >> >>>> List with numerous bullets beneath it. >>>> >>>> >>> Yes, this is an FPGA with a serial port on it? The is >>> >> your universal >> >>> JTAG TAP emulator, which gives feedback about the path than >>> >> an actual >> >>> TAP is traversing. >>> >>> Without a device to connect to, one that gives responses >>> >> back, how do >> >>> you verify success? >>> A JTAG Tap is interesting. It can be put in chain and collect datas inside.
The JTAG emulator have to commnunicate over the JTAG byself. No serial port. A RAM behind collects and readout over the JTAG. The goal of JTAG is to communicate to all IC also to the emulator. Before starting such emulator, the SVF or XSVF insid openocd have to be ready. The emulator can reprogrammed for new TAP interf >> Functional unit testing could be a start. We could exercise >> a ton of code without ever needing to talk to the hardware. >> That was what I was thinking when I added the items to The List. >> >> A device like you describe could definitely be used for >> deeper testing, and it's not a particularly bad idea. I have >> been meaning to get into synthesizing my own FPGAs, and this >> sounds like a fairly easy and useful starter project. It is >> now on The List as well, unless you are now going to tell me >> why my child-like ignorance has led me astray. >> >> You may have well just tempted me with Pandora's box. I must >> know more. >> > > I'm not sure whether this is a good idea. There are many combinations of > JTAG dongles and processors. The JTAG TAP interface is least of the > problems when dealing with JTAG. The problem is always in the layers > behind the JTAG interface. If you want to develop a test suite you'll > need to simulate all the supported CPUs, flashes, etc. Worse, a > simulator is never 100% like the real thing. More worse, JTAG seems to > be the last thing on the list to implement on a chip so implementations > often contain bugs and other undocumented mayhem which may be different > between devices in the same family and/or steppings (device revisions). > > In others words: nothing beats testing with a real target and there will > always be new devices that require some patching. > > Another item for the list: With some imagination it would be possible to > simulate a UART or an SPI interface using the JTAG dongle. Maybe even > bit I/O using the RST en TRST pins. This would allow extending OpenOCD > into a universal programmer for microcontrollers. > > SPI is a nice feature to program serial Flash This would be create.# Rene
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