EEVblog #1127 - Mailbag Monday

[mrpackethead]

I figure this will be the best USB scope ever. Everyone is going to contribute to make it perfect.  Maybe Dave will be moved. Maybe this will proove the value of opensource Hardware.

[FrankBuss]

you don't need to connect D0-D7 of the external bus to D0-D7 of the RAM IC, because it doesn't matter, if the RAM data bit 7 is accessed by the bus data bit 3.

I hate when people do this, because it makes debugging a nightmare when the only accessable data bus pins are in the wrong order.

McBryce.

For my Vectrex cartridge I connected even the address bus of a flash in an arbitrary way, works great 



And routing was much easier, because of the KiCad push-and-shove function. The old Eagle version I used for my Kerberos board didn't have it, manual routing was a nightmare. Only problem was that KiCad doesn't have pin-swap, so I had to "emulate" it by using labels in the circuit diagram for all connections and then moving the labels, re-exporting and importing the netlist etc.



Maybe someday I will switch to a professional program like Altium CircuitStudio. I recently installed Altium Studio (again after I gave it a trial some years ago). Just with a free viewer license, because a client used it to design a board I'm writing the firmware for, and it looks really good.

[GeorgeOfTheJungle]

I also cross the address lines :-)

[BrianHG]

you don't need to connect D0-D7 of the external bus to D0-D7 of the RAM IC, because it doesn't matter, if the RAM data bit 7 is accessed by the bus data bit 3.

I hate when people do this, because it makes debugging a nightmare when the only accessable data bus pins are in the wrong order.

McBryce.

Hun, how do you expect the ram's DQStrobe groups and write masks at every 4 bits to line up and function right?
As for messing with the address lines, how do you expect extended page bursts and proper enhanced bank interleaving to function correctly giving continuous 0 wasted data buss cycles when using bank-interleaved ram access?

I can see how you can get away with a small static ram IC access.  You can also at some level do it with DDR2/DDR3 ram on the basis the FPGA doesn't have dedicated DQStrobe for certain IO pin groups to get the highest FMAX out of your DDR IO ports.  Complete careless random swaps are no longer good enough unless you are using 1x DRAM with a fixed burst size and want to re-RAS/CAS cycle every new read or write instead of enhance smart 1 full page access only re-issuing a new RAS only when crossing a page boundary or refresh is required.

[GeorgeOfTheJungle]

EPROMs don't seem to care :-)

[FrankBuss]

Right, no problem for old-school EPROMs, flash and static RAM Except for the flash there was a minor twist, that there are special commands implemented by writing to special addresses for flashing and erasing, which I had to remap in the programmer. And you can't do meaningful block erase, but there is a chip erase command as well, and there is only a single byte flashing command.

[EEVblog]

Asking the important questions here, but does anyone know about the red t-shirt Dave wears in this video? I'm really digging the design...

It's the EFF "Freedom Cat"
https://supporters.eff.org/t-shirt-size-chart

[pshersby]

I have this screwdriver and I do use it quite a lot for repair work.  It is nice to habve a standard size screwdriver on the bench and be able to swap bits without it turniong into a pile of odd screwdrivers,  As well as the basic kit, I picked up a separate kit with normal handle from wiha because it was the cheapest way of getting all the extra 6mm hex fitting bits and something to store them in, it also means I can have the frequent use bit in the speede and another bit in the normal handle.

In terms of shape, build an tip quality really happy.

First problem Forget the price of the system, this is how wiha really make money!!!!! --> only 6mm hex bits fit NOT 1/4 inch, and the wiha bits are pricey,  I had to order a separate T8 bit,  (I think WERA might also be doing some 6mm bits now, but just flat, pozi, philips and a small range of torx, none of the other security bits etc).  The Wiha range is really limited.
Next - slow turning, but fast enough - however slow gearing should mean plenty of torque so it can undo screws, but it is hopeless for that - I need to start almost every screw manually then engage the power,  and if you try to be clever and simultaneously operate the ring switch, then it detects overcurrent, switches off, so you do not get austomatic transition from turning manually to turning by power, you have to relase the switch and re-enable - it annoys me every time!

So I've got one, i use it, I like Wiha drivers, but won't buy from these guys again, over priced driver, limited bits, and locked into expensive Wiha 6mm hex fittings - I pay good money for good product, but this leaves a bad taste.  Buy something else.