POC VERSION TWO

[BigDumbDinosaur]

BigDumbDinosaur wrote:

In the process of sorting out this current mess, I accidentally downloaded the data sheet for the 28L202 DUART...and discovered that its write-up on the interrupt arbitration makes more sense...reading it...made me suspect that some type of non-zero value must be written into the ICR to activate interrupt arbitration, which I haven't done up until now...So the new plan of attack is to work out proper values for the ICR and BCRs (bidding control registers), add them to the setup data tables, and see if things start working.

Some progress to report. I was able to get the timer in the QUART's A-block to generate an IRQ that can be serviced. Timer A is responsible for making the jiffy IRQ functional, which is important to the overall function of the firmware. So this is a significant step forward. I'm currently observing the IRQ pulse train with a logic probe, and it appears that the IRQ is happening at the right rate.

I'm not out of the woods yet with this thing. I haven't solved the mystery of how to make receiver and transmitter IRQs work and I also have to concoct a method of dealing with a receiver overrun, as that generates a separate IRQ that will persist until the overrun status in the QUART channel is reset. However, I do know now how to set up the basic interrupt logic in the QUART, so I soon expect to see serial I/O working.

[jgroth]

BigDumbDinosaur wrote:

Aslak3 wrote:

I've only seen ZIFs with rectangular pins; I assume your one has round pins?

It does, 18 mil pins, to be exact. It took some searching to find this socket but has worked out well.

I've been searching for one those myself but haven't found anything. I can see in the photo that manufacturer is Aries Electronics but what part number though? Where did you buy yours?

[GaBuZoMeu]

jgroth wrote:

BigDumbDinosaur wrote:

Aslak3 wrote:

I've only seen ZIFs with rectangular pins; I assume your one has round pins?

It does, 18 mil pins, to be exact. It took some searching to find this socket but has worked out well.

I've been searching for one those myself but haven't found anything. I can see in the photo that manufacturer is Aries Electronics but what part number though? Where did you buy yours?

Aries ZIF sockets are listed at Digikey. ECE manufactures ZIF sockets as well. Their pins are 0.7mm wide. Datasheet: http://www.tme.eu/en/Document/9a2ede4c5 ... series.pdf


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edit(1): DS link added

[BigDumbDinosaur]

jgroth wrote:

BigDumbDinosaur wrote:

Aslak3 wrote:

I've only seen ZIFs with rectangular pins; I assume your one has round pins?

It does, 18 mil pins, to be exact. It took some searching to find this socket but has worked out well.

I've been searching for one those myself but haven't found anything. I can see in the photo that manufacturer is Aries Electronics but what part number though? Where did you buy yours?

The socket I use is Aries part number 28-6554-11. I got it from Mouser Electronics. Data sheet attached.

[BigDumbDinosaur]

GaBuZoMeu wrote:

ECE manufactures ZIF sockets as well. Their pins are 0.7mm wide. Datasheet: http://www.tme.eu/en/Document/9a2ede4c5 ... series.pdf

0.7 mm pins are too thick to be safely inserted in most DIP sockets. The Aries part I use has 18 mil round pins, roughly 0.45mm.

[jgroth]

BigDumbDinosaur wrote:

jgroth wrote:

BigDumbDinosaur wrote:

Aslak3 wrote:

I've only seen ZIFs with rectangular pins; I assume your one has round pins?

It does, 18 mil pins, to be exact. It took some searching to find this socket but has worked out well.

I've been searching for one those myself but haven't found anything. I can see in the photo that manufacturer is Aries Electronics but what part number though? Where did you buy yours?

The socket I use is Aries part number 28-6554-11. I got it from Mouser Electronics. Data sheet attached.

Thank you.

[BigDumbDinosaur]

BigDumbDinosaur wrote:

I'll tell you...I'm really tempted to whip up a design using the ATF1508AS and two (maybe four) 29L92s. Those UARTs work great and with 16 deep FIFOs, they don't bang away at the MPU with IRQs like some other UARTs. However, POC V2 has to be made operative before anything new can be designed. It's a rule around here!

The above was from November 2016. I really hate eating my own words, but it's time to open wide and starting the mastication process. POC V2, revision 0, is history. I've invested way too much time into trying to get that #*&$@*%^! QUART to work and have decided to put the computer on the shelf and let it collect dust.

[whartung]

So are you going to do a new board, with different UARTs?

As a complete, random, aside BDD.

I downloaded Wine for my Mac, and was able to run the ExpressPCB software. And I went to their online library or gallery or whatever it is. And the first thing it pulled up, no searching, just the first thing that showed up -- was the POC V2 board and schematic.

[BigDumbDinosaur]

whartung wrote:

So are you going to do a new board, with different UARTs?

I'm working on a redesign using two 28L92s.

[Aslak3]

BigDumbDinosaur wrote:

I'm working on a redesign using two 28L92s.

Are there no other Quads that are suitable? I've personally had good success with the SC16C654. Admittedly I doubt it's in production, but how much of a concern is that?

[BigDumbDinosaur]

Aslak3 wrote:

BigDumbDinosaur wrote:

I'm working on a redesign using two 28L92s.

Are there no other Quads that are suitable? I've personally had good success with the SC16C654. Admittedly I doubt it's in production, but how much of a concern is that?

The 16C654 doesn't have the timer(s) present in the NXP 26C/28C UARTs, so I can't use it in my design.

[8BIT]

BigDumbDinosaur wrote:

POC V2, revision 0, is history. I've invested way too much time into trying to get that #*&$@*%^! QUART to work and have decided to put the computer on the shelf and let it collect dust.

Hey BDD,

Do you feel like sharing any of your code associated with the DUART? I'd hate to see POC V2 rev0 shelved. I would like to have look.

Daryl

[BigDumbDinosaur]

8BIT wrote:

BigDumbDinosaur wrote:

POC V2, revision 0, is history. I've invested way too much time into trying to get that #*&$@*%^! QUART to work and have decided to put the computer on the shelf and let it collect dust.

Hey BDD,

Do you feel like sharing any of your code associated with the DUART? I'd hate to see POC V2 rev0 shelved. I would like to have look.

Daryl

POC V2 rev 0 uses a QUART. Is that what you meant?

[8BIT]

Yes, sorry, my muscle memory hit D vs. Q. If you want to share, I'd be interested in having a look.

Daryl

[BigDumbDinosaur]

8BIT wrote:

Yes, sorry, my muscle memory hit D vs. Q. If you want to share, I'd be interested in having a look.

Daryl

I'll have to post the entire firmware code, as it's spread out over many INCLUDE files—it's not practical to isolate just the QUART driver. If you are still interested let me know.

I've all but completed the design and PCB layout for POC V2, revision 1, which will use a pair of 28L92 DUARTs connected to MAX238s, instead of the MAX248 in revision 0. Although use of the MAX238s increases the total parts count, it turned out to be better in terms of the PCB layout.

While I was at it, I added some minor circuit refinements, reduced the number of discrete resistors, and changed the PCB layout around the 65C816 and the two SRAMs, the latter resulting in some slightly shorter circuit paths. I should have this mess ready for posting soon.