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SubjectE & Q timing on M6809 Reply to this message
Posted bysellenoff
Posted on08/09/04 06:15 PM



Was wondering if someone could help me understand how to calculate the timing of these 2 signals from the 6809.

Assuming the external crystal is set to drive the 6809 @ 8Mhz (which i believe is the top speed the chip can go - on the 68B09), what would the frequency of the E & Q lines be?

The hardware i'm looking at uses E to pulse a 4020 counter which eventually toggles the FIRQ of the 6809, and obviously I'm trying to calculate the correct freq. to generate the firq.

I've looked over the 6809 datasheet and just don't really follow it. I've never been good with timing in general, and those datasheets are not written to be easily understandable unless you already get the concept! :)

So if someone could explain, not only the answer, but how I could have derived the answer from looking at the datasheet, it would be greatly appreciated..

Thanks
-Steve




SubjectSounds suspiciously like a homework question :) *nt* new Reply to this message
Posted byBart T.
Posted on08/09/04 11:55 PM



> Was wondering if someone could help me understand how to calculate the timing of
> these 2 signals from the 6809.
>
> Assuming the external crystal is set to drive the 6809 @ 8Mhz (which i believe
> is the top speed the chip can go - on the 68B09), what would the frequency of
> the E & Q lines be?
>
> The hardware i'm looking at uses E to pulse a 4020 counter which eventually
> toggles the FIRQ of the 6809, and obviously I'm trying to calculate the correct
> freq. to generate the firq.
>
> I've looked over the 6809 datasheet and just don't really follow it. I've never
> been good with timing in general, and those datasheets are not written to be
> easily understandable unless you already get the concept! :)
>
> So if someone could explain, not only the answer, but how I could have derived
> the answer from looking at the datasheet, it would be greatly appreciated..
>
> Thanks
> -Steve
>


----
Bart


SubjectRe: Sounds suspiciously like a homework question :) *nt* new Reply to this message
Posted bysellenoff
Posted on08/10/04 12:22 PM



Thanks for nothing Bart T!

It's not a homework question, unless you think someone who's 32 years old still has homework to do! Maybe I need to post a copy of my driver's license and passport to get a question answered!?

It's quite a sorry situation when that's the first and only response to someone asking for help! I've seen it before in forums all over, and sometimes it is obvious that a student is trolling to get free homework done, but I still think people should be given the benefit of the doubt.

Sorry if I sound pissed, but I am quite insulted by your response. I only wish I *did* get an education in any of this stuff when I was in school, then I wouldn't need to be asking for help.

FWIW - I'm not a newbie to emulation, digital circuits, or hardware.. (see www.pinmame.com for the majority of my work, plus some drivers for mame & fixing up a cpu core for mess(tms7000)) but the problem is it was all *self taught* in my limited spare time, and as such, there are glaring gaps in my understanding of certain things.

The question comes from sound board hardware for an Alvin G & Co. pinball machine which I am trying to improve the existing emulation I did. The current music plays too slowly, yet the samples play too fast. I've mucked around with guessing a combination of CPU Freq & FIRQ rate, and can't seem to get something quite right..

Having recently gotten access to a manual, I thought I'd try and figure it out from the schems. So I grabbed hold of the 6809 datasheet and did some reading, but I just don't understand the very brief explanation. That's where the question comes from...

I would very much appreciate some kind of help!
-Steve




> > Was wondering if someone could help me understand how to calculate the timing
> of
> > these 2 signals from the 6809.
> >
> > Assuming the external crystal is set to drive the 6809 @ 8Mhz (which i believe
> > is the top speed the chip can go - on the 68B09), what would the frequency of
> > the E & Q lines be?
> >
> > The hardware i'm looking at uses E to pulse a 4020 counter which eventually
> > toggles the FIRQ of the 6809, and obviously I'm trying to calculate the
> correct
> > freq. to generate the firq.
> >
> > I've looked over the 6809 datasheet and just don't really follow it. I've
> never
> > been good with timing in general, and those datasheets are not written to be
> > easily understandable unless you already get the concept! :)
> >
> > So if someone could explain, not only the answer, but how I could have derived
> > the answer from looking at the datasheet, it would be greatly appreciated..
> >
> > Thanks
> > -Steve
> >
>
>
> ----
> Bart
>





SubjectRe: Sounds suspiciously like a homework question :) *nt* new Reply to this message
Posted byRiff
Posted on08/10/04 08:21 PM



> > > Assuming the external crystal is set to drive the 6809 @ 8Mhz (which i
> believe
> > > is the top speed the chip can go - on the 68B09), what would the frequency
> of
> > > the E & Q lines be?
> > >
> > > The hardware i'm looking at uses E to pulse a 4020 counter which eventually
> > > toggles the FIRQ of the 6809, and obviously I'm trying to calculate the
> > correct
> > > freq. to generate the firq.
> > >
> > > I've looked over the 6809 datasheet and just don't really follow it. I've
> > never
> > > been good with timing in general, and those datasheets are not written to be
> > > easily understandable unless you already get the concept! :)
> > >
> > > So if someone could explain, not only the answer, but how I could have
> derived
> > > the answer from looking at the datasheet, it would be greatly appreciated..
> > >
> > > Thanks
> > > -Steve
> > >
> >

If you look at Figure 10 - Clock Generator in the Motorola 6809 Technical Data manual, you will notice that E and Q are both nominally half the frequency of the input XTAL frequency. If XTAL is nominally 8 Mhz, E is nominally 4 Mhz. Looking at the clock generator example you should also be aware that it is not always the case that E and Q are always half the frequency of XTAL. In the clock generator circuit, an extra flip-flop is used to generate a signal which adds wait states, causing the duty cycle of E and Q to be stretched out. There may be a limit to how long E and Q can be stretched out. If a 6908B is being used then you don't need to worry about it as the E and Q pins are outputs. The E and Q inputs are meant to provide a means of external synchronization, but I'd have to read through the 6809 manual again to be sure that the internally generated E and Q signal frequencies are constant. If they werent, they probably wouldnt be used for triggering sound generation, so its probably not an issue, allowing for the assumption that they are always clocked at half the frequency of the oscillator input.


SubjectRe: Sounds suspiciously like a homework question :) *nt* new Reply to this message
Posted byBart T.
Posted on08/10/04 09:12 PM



> It's quite a sorry situation when that's the first and only response to someone
> asking for help! I've seen it before in forums all over, and sometimes it is
> obvious that a student is trolling to get free homework done, but I still think
> people should be given the benefit of the doubt.

Settle down. I'm sorry for the rude comment but it wasn't really intended that way (hence the smiley.)


----
Bart


SubjectRe: Sounds suspiciously like a homework question :) *nt* new Reply to this message
Posted bysellenoff
Posted on08/10/04 11:53 PM



Thanks Riff!

Yes, it is the 68B09, and i'm glad you pointed out that the previous versions of the chip showed E & Q as inputs, since I was quite confused when 2 different sets of data sheets showed the pins differently..

I'll check out seeing how it sounds with 1/2 the freq, thanks!


> If you look at Figure 10 - Clock Generator in the Motorola 6809 Technical Data
> manual, you will notice that E and Q are both nominally half the frequency of
> the input XTAL frequency. If XTAL is nominally 8 Mhz, E is nominally 4 Mhz.
> Looking at the clock generator example you should also be aware that it is not
> always the case that E and Q are always half the frequency of XTAL. In the
> clock generator circuit, an extra flip-flop is used to generate a signal which
> adds wait states, causing the duty cycle of E and Q to be stretched out. There
> may be a limit to how long E and Q can be stretched out. If a 6908B is being
> used then you don't need to worry about it as the E and Q pins are outputs. The
> E and Q inputs are meant to provide a means of external synchronization, but I'd
> have to read through the 6809 manual again to be sure that the internally
> generated E and Q signal frequencies are constant. If they werent, they
> probably wouldnt be used for triggering sound generation, so its probably not an
> issue, allowing for the assumption that they are always clocked at half the
> frequency of the oscillator input.
>





SubjectRe: Sounds suspiciously like a homework question :) *nt* new Reply to this message
Posted bysellenoff
Posted on08/10/04 11:56 PM



Bart T - I'm sorry also for over-reacting bit. I've been under a ton of stress lately, so my patience (already limited by genetics) is very thin these days..

I was really excited to see a reply to my question, and then really bummed out to see the response. Since I was already having a terrible day, it just burst my bubble.


> > It's quite a sorry situation when that's the first and only response to
> someone
> > asking for help! I've seen it before in forums all over, and sometimes it is
> > obvious that a student is trolling to get free homework done, but I still
> think
> > people should be given the benefit of the doubt.
>
> Settle down. I'm sorry for the rude comment but it wasn't really intended that
> way (hence the smiley.)
>
>
> ----
> Bart
>





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