Manual zz. The device features three enable inputs E1, E2 and E3. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC. Ordering information Table 1.
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Adressbit 15 is used as G1 on the 3 to 8 decoder. I want to achieve the following outputs:. CS0 0xB However I got a permanent High signal on every output. That wiring is absolutely correct. Einstein was right: "Two things are unlimited: the universe and the human stupidity. But i'm not quite sure about the former Hmm I may be able to test it after getting some longer wires for my breadboard since I currently don't have any at home. Is it possible that the pulses on the input of the Chip are too short for whatever reason I only got a XProtolab at home and on that screen the pulses look really ugly.
It all looks good to me too. I have used this type of memory decoding with a on many different types of processors, but never the AT90USB If so, do that, then write a simple loop to walk-thru the 16 state possiblilities which scoping or DVMing in a static, or near-static, condition.
That exercise will at least tell you that your wiring matches your schematic. If there is a wiring mixup, you'll stand a better chance of deducing it under static conditions than with 16MHz pulses. Lee -. How did the serpent move around before the fall? How are you measuring those?
Quote: However I got a permanent High signal on every output. I got one of these fantastic XProtolabs from Gabotronics which means I can only measure roughly at this frequency but I see peaks on the correct Pins. Quote: Quote: However I got a permanent High signal on every output. Yes that's what I assumed aswell.
G2A and G2B are hardwired to Ground as shown in the schematic and measured aswell. Mr Moonlight, glitches on the outputs of the are unevitable in this HW setup. You need some gating signal that tells when an address is valid. It depends on what you plan to connect to the outputs of the Dragon broken?
Quote: I got one of these fantastic XProtolabs from Gabotronics which means I can only measure roughly at this frequency While they are a nice device, I would not call it a definitive test. Quote: but I see peaks on the correct Pins. But are the peaks valid logic signals? I suspect so! If that gives you you outputs, perhaps a pull-up 4. Nard brings up a good point if you are going to address memory.
Quote: You need some gating signal that tells when an address is valid. The output of the controls the CS for an A. A0-A1 are used as inputs to the A on this extension card whereas AA15 are used to chose between different cards different CS. Plons wrote: [ Quote: Quote: but I see peaks on the correct Pins. I can't test that at home. I will have the chance on Tuesday. Quote: The output of the controls the CS for an A. Rd and Wr on the A will take care of the rest. Btw, I had to consult an old Intel databook: And the typical smell brought back memories If the boards are more than cm away from the AVR, put resistors in series and cap's to ground on all signals going to those boards: AVR's and HC T logic have larger slewrate values then the old stuff.
The OP may have to resort to using bit bashing to implement the bus interface. To see if the decoder is working, use a flipflip or d type latch clocked by the select output and put a led or two on the output. Quote: were not too fast at the gest of times.
But I checked the Intel databook and the datasheet of the ; with the info that the is running at 2MHz, my conclusion is that Moonraker is in the clear :. It seems that the can't handle that speed. This seems way too slow for this device. This was measured when nothing was connected to the output of the The NXP datasheet claims a max.
Which would result in a frequency of 25MHz. Or is the propagation delay the wrong parameter? Do I really need to do this? G1 is already connected to A Quote: Do I really need to do this?
Can you post the complete schematic and the test SW? Edit: 2 NOP delay?? Are you writing to the IO-ports instead of using the external memory interface? Plons wrote: Quote: Do I really need to do this? Ok I'll try that. Yes HCT. I'll fix it. Quote: Yes I tested everything by writing to the IO-ports because it worked with static levels But my dear fellow, direct accessing the IO-port is a completely different way of "cooking".
You will need the external memory interface when you want to control the A's. PS1 We need the underlying assembler code when we discuss timing PS2 With the program as posted, can you post scope-picture of the output? And that should be no problem for the No NOP's required.
The 16MHz shouldn't be a problem for the either right? What is the baudrate and what value is in the baudrate register?
Quote: The 16MHz shouldn't be a problem for the either right? Now you got me puzzled. And that should be 2MHz as you mentioned earlier because that is what you need for external memory timing. The A's need appr. At 16MHz, the period is I suggest you stick with assembler when sorting out things like this.
Or at least have a look at the reulting assemblercode. Baudrate is the Registers are set accordingly I hope so ;. Or at least have a look at the resulting assemblercode.
All the IO-Port tests are done with the A disconnected. To evaluate the problem with the step by step.
Just wanted to make sure we're on the same track. And becuase of the slow response: are you positive that the is supplied with 5V and that there is a cap of 0. Common grounds? These questions may look silly but need to be asked. I was indeed wondering whether the was actually powered, and not just operating on leakage from its input logic signals. I get a lot of this sort of thing at work and it's quite confusing when you turn the power off on a unit and the damn thing keeps right on working Neil Barnes www.
It seems that it was only a soldering issue However I'm still having issues interfacing the A. Writing doesn't work at all and Reading works only for Bit0-Bit5. I'll open another thread for it tonight if I can't figure it out. Quote: However I'm still having issues interfacing the A. How is the external memory setup in the ?
And how long are the wires from to the A's? Well I thought about a new thread because the works now. I had a look at the dissassembly and found exactly what expected.
The reading part works with one flaw only Bit are valid Bit 6 and 7 always read as 0 and there is a really strange signal on those lines.
74HC138; 74HCT138 3-to-8 Line Decoder, Demultiplexer; Inverting
74HCT138N Philips Semiconductors, 74HCT138N Datasheet
74HC138; 74HCT138 1. General description 3-to-8 line decoder/demultiplexer; inverting