Question about BE/RDY pin and WDC

[cbmeeks]

I read this from the primer (Mystery Pins):

http://wilsonminesco.com/6502primer/MysteryPins.html

Quote:

BE: The bus-enable input allows external control of the buses. If you don't want to further investigate this possibility through other sources, then pull this up to +5V through a 3.3K resistor. You'll only find this pin on WDC's 65c02's anyway, not on those of other manufacturers.

So....If I want my board to work with any 65C02, and I only care about 65C02 in general (no NMOS), then should I bother putting a jumper for the BE pin to a 3.3k pull-up?

I only have WDC 65C02. Or, should I just go ahead and tie that pin to the 3.3k pull-up anyway?

Also, I *DO* want to eventually use this pin with some micro-controllers. If that makes a difference...

EDIT:

Also, I have the same question about the RDY pin. According to the primer and the datasheet:

Quote:

RDY: The "ready" input is used for single-stepping, wait states for slow memory, and DMA. Some makes of 65c02 have had internal weak pull-ups on RDY and other inputs, so you could get away without connecting it to anything. WDC has apparently removed this. Better not let it float. Note that WDC's RDY is bidirectional, and it will be pulled low if it gets the WAI (wait-for-interrupt) instruction in your program. (WAI puts the processor in a better position to make a fast-as-possible response to an imminent interrupt.) On the other hand, although you may not have any plans to use WAI, a crash could make the processor misinterpret a $CB operand or data byte as the WAI op code and possibly damage the chip through heating problems if the output is shorted to +5V. If you don't want to further investigate or use the features this pin is made for, and you want the circuit to be able to handle any manufacturer's 6502 or 65c02, pull it up to +5V through a 3.3K pull-up resistor.

It seems that you may not always want to put the RDY pin directly to a 3.3k pull-up as some users may want to drive it directly.

So, would you recommend I put a jumper from the RDY pin and 3.3k pull-up as well?

BTW, this is for a proto-type board for the 65C02 and not a SBC, per se.

Thanks.

[BigDumbDinosaur]

cbmeeks wrote:

I read this from the primer (Mystery Pins):

http://wilsonminesco.com/6502primer/MysteryPins.html

Quote:

BE: The bus-enable input allows external control of the buses. If you don't want to further investigate this possibility through other sources, then pull this up to +5V through a 3.3K resistor. You'll only find this pin on WDC's 65c02's anyway, not on those of other manufacturers.

So....If I want my board to work with any 65C02, and I only care about 65C02 in general (no NMOS), then should I bother putting a jumper for the BE pin to a 3.3k pull-up?

I don't see any reason to jumper your BE connection. Best to tie it to Vcc with a pull-up. If you later decide to control BE with other hardware the resistor won't get in the way, as any 74HC or 74AC device can readily sink the approximate 1.5 mA that would have to be drawn to pull BE to ground.

Quote:

Also, I have the same question about the RDY pin...It seems that you may not always want to put the RDY pin directly to a 3.3k pull-up as some users may want to drive it directly.

Again, the pull-up won't get in the way if you decide to externally control RDY, as would be the case if generating wait-states.

[BigEd]

If you want to support different suppliers, cbmeeks, as you say you do, then yes it looks like you'll need a jumper: pin 36 on the Rockwell part at least is described as 'No Connect'

There's no substitute for datasheets!
http://archive.6502.org/datasheets/rock ... essors.pdf
http://www.westerndesigncenter.com/wdc/ ... 65c02s.pdf

But, as ever, the more you consider possible flexibility and expansion, the more work you do now, which might not be needed. Best not to anticipate too many possibilities.

(It's possible that tying a No Connect pin high will be harmless, but that wouldn't be a normal approach.)

[cbmeeks]

Thanks for your suggestions.

I may just leave out the jumpers to keep things simple.

I have read the data sheet for the WDC as that's the only 65C02's I have (not counting the 6502's in my many computers).

Are the Rockwell versions even made any more?

[BigEd]

Sorry, I was noting your
> If I want my board to work with any 65C02
and assumed you had something in mind. Only WDC parts could be bought new, but someone might have the others, or indeed you might be able to buy them as reclaims.

Synertek also made one, see the second part of
http://chidesters.org/scott/meadow/sy6502.pdf

[cbmeeks]

Oh, no worries. I wasn't complaining.

I'd like my board to be generic so I may have to put the jumpers in anyway. No big deal. The only thing I'm 100% on is that it must be a CMOS version.

Stay tuned...

[BigDumbDinosaur]

cbmeeks wrote:

Are the Rockwell versions even made any more?

Only WDC is producing 65C02s at this time. Any Rockwell devices for sale are either pulls or NOS, with the latter rapidly disappearing. At this point in time, there is little reason to use the Rockwell part (and no reason to use an NMOS 6502, except for historical purposes), as the WDC part, which is technically superior, is readily available for not much more than the Rockwell item.

Historical note: many Rockwell 65C02 pulls came out of old modems from back when modems had discrete components. When V.90 modems became available in the latter 1990s, a lot of V.34 modems suddenly became obsolete and unsaleable, as V.90 almost doubled the theoretical download speed over V.34. Liquidators purchased V.34 modems from distributors for pennies on the dollar—or pound, extracted the "good" chips from them and scrapped the rest of the parts.

[jac_goudsmit]

As the others already said, a jumper on pin 36 (BE) is probably not necessary. But don't forget a jumper between pin 1 and GND: on WDC this is an output pin (which you can leave disconnected by removing the jumper), but on the other ones it needs to be grounded.

For more hints see http://www.westerndesigncenter.com/wdc/ ... ements.cfm

===Jac

[cbmeeks]

jac_goudsmit wrote:

As the others already said, a jumper on pin 36 (BE) is probably not necessary. But don't forget a jumper between pin 1 and GND: on WDC this is an output pin (which you can leave disconnected by removing the jumper), but on the other ones it needs to be grounded.

For more hints see http://www.westerndesigncenter.com/wdc/ ... ements.cfm

===Jac

Way ahead of ya.

Yep, I'm certainly putting a jumper on that one. I don't think it's going to take much work to support other 'C02's so I'm going to lean in that direction.

Thanks.