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Messages from 160100

Article: 160100
Subject: Re: fpga zigbee interface
From: David Wade <g4ugm@dave.invalid>
Date: Thu, 25 May 2017 17:42:10 +0100
Links: << >>  << T >>  << A >>
On 25/05/2017 14:05, BobH wrote:
> On 05/24/2017 10:16 PM, srirameee09@gmail.com wrote:
>> i have spartan6 atlys(LX45) board, can anyone suggest me how to 
>> interface zigbee to this board to communicate with pc.thnx
>>
> 
> Buy a Zigbee module and implement whatever physical layer it needs. 
> Freescale/NXP probably offers some. Texas Instruments may also.
> 
> Any particular reason for using Zigbee? Bluetooth would probably be 
> easier to find modules for and probably has better support on the PC end.
> 
> BobH

As this is a Student board perhaps that's a requirement of a college 
project or similar. Plenty of papers on the net on doing this for 
specific data items e.g.

http://iopscience.iop.org/article/10.1088/1742-6596/332/1/012007/meta

plenty of simple modules that use for example the SPI interface e.g.

http://www.microchip.com/wwwproducts/en/MRF24J40MA

which is simple to implement, but that board already has lots of 
connectivity. Why complicate things by add ZigBee

Dave

Article: 160101
Subject: ZAP : An open source ARM processor (feedback)
From: revanth91kamaraj@gmail.com
Date: Sun, 28 May 2017 05:45:37 -0700 (PDT)
Links: << >>  << T >>  << A >>
Hi,

I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.

Would like your feedback/criticism of the project.

Thanks,
K Revanth

  

Article: 160102
Subject: ZAP : An open source ARM processor (feedback)
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Sun, 28 May 2017 09:10:09 -0700 (PDT)
Links: << >>  << T >>  << A >>
Awesome.  I look forward to looking at your work.

Thank you,
Rick C. Hodgin

Article: 160103
Subject: Re: ZAP : An open source ARM processor (feedback)
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Sun, 28 May 2017 10:15:14 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Sunday, May 28, 2017 at 8:45:44 AM UTC-4, Revanth Kamaraj wrote:
> Hi,
> 
> I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.
> 
> Would like your feedback/criticism of the project.

What can you advise me to do / look at for testing your core?

Thank you,
Rick C. Hodgin

Article: 160104
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Sun, 28 May 2017 17:44:53 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Sunday, May 28, 2017 at 10:45:20 PM UTC+5:30, Rick C. Hodgin wrote:
> On Sunday, May 28, 2017 at 8:45:44 AM UTC-4, Revanth Kamaraj wrote:
> > Hi,
> > 
> > I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.
> > 
> > Would like your feedback/criticism of the project.
> 
> What can you advise me to do / look at for testing your core?
> 
> Thank you,
> Rick C. Hodgin

Hi,

More test cases could be added to the core to thoroughly test it. See the sw/tests directory. Test cases may be easily added (the documentation describes how to add test cases).

One of the main things left to do is to build a basic Wishbone SoC around the core consisting of some simple peripherals (UARTs, GPIO, Interrupt Controller) etc. 

Thanks,
Revanth

Article: 160105
Subject: Re: ZAP : An open source ARM processor (feedback)
From: rickman <gnuarm@gmail.com>
Date: Mon, 29 May 2017 01:44:18 -0400
Links: << >>  << T >>  << A >>
revanth91kamaraj@gmail.com wrote on 5/28/2017 8:45 AM:
> Hi,
>
> I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.
>
> Would like your feedback/criticism of the project.

I am curious.  Has this been up long?  I remember some years ago, maybe as 
far back as 2002 ballpark, someone wrote code for an ARM7 I think.  He 
posted the code on opencores if I recall correctly.  It was only up a month 
or so and he received an invitation from ARM to discuss his code.  That 
means he got a call from an ARM lawyer.  Seems there are parts of the ARM 
architecture that are patented.  At that time it would have been very hard 
to design around the patent.  I think it was related to interrupt 
acknowledgement.

Again, if I recall correctly, ARM asked him to remove his code, but included 
a sweetener, they offered him a job!  So the code is gone.  I'm sorry I 
never downloaded a copy, but it is unlikely I would have bothered to build 
it, so no great loss.

That particular patent may have expired.  But you can be sure there are 
others that are still in force.  Otherwise, what would stop companies from 
writing their own ARM processors and not paying ARM a royalty?

I just looked up ARMv4T and that is the same instruction set as the ARM7T. 
With a 10 stage pipeline I guess your design is more like the ARM9T.  If 
this is the same instruction set, it must have the same interrupt 
acknowledge design, no?  If the patent has expired you may be home free.

Hmmm, while researching my facts for this I found a reddit page where you 
talk about patents and other things last December.  So I guess none of this 
is news to you.  :)   But that conversation was for the ARMv4 instruction 
set, not the ARMv4T.  Any patent surprises there?  I guess the ARMv4T is 
also beyond patent expiration dates, no?

-- 

Rick C

Article: 160106
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Mon, 29 May 2017 07:20:58 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Monday, May 29, 2017 at 11:14:25 AM UTC+5:30, rickman wrote:
> revanth91kamaraj@gmail.com wrote on 5/28/2017 8:45 AM:
> > Hi,
> >
> > I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.
> >
> > Would like your feedback/criticism of the project.
> 
> I am curious.  Has this been up long?  I remember some years ago, maybe as 
> far back as 2002 ballpark, someone wrote code for an ARM7 I think.  He 
> posted the code on opencores if I recall correctly.  It was only up a month 
> or so and he received an invitation from ARM to discuss his code.  That 
> means he got a call from an ARM lawyer.  Seems there are parts of the ARM 
> architecture that are patented.  At that time it would have been very hard 
> to design around the patent.  I think it was related to interrupt 
> acknowledgement.
> 
> Again, if I recall correctly, ARM asked him to remove his code, but included 
> a sweetener, they offered him a job!  So the code is gone.  I'm sorry I 
> never downloaded a copy, but it is unlikely I would have bothered to build 
> it, so no great loss.
> 
> That particular patent may have expired.  But you can be sure there are 
> others that are still in force.  Otherwise, what would stop companies from 
> writing their own ARM processors and not paying ARM a royalty?
> 
> I just looked up ARMv4T and that is the same instruction set as the ARM7T. 
> With a 10 stage pipeline I guess your design is more like the ARM9T.  If 
> this is the same instruction set, it must have the same interrupt 
> acknowledge design, no?  If the patent has expired you may be home free.
> 
> Hmmm, while researching my facts for this I found a reddit page where you 
> talk about patents and other things last December.  So I guess none of this 
> is news to you.  :)   But that conversation was for the ARMv4 instruction 
> set, not the ARMv4T.  Any patent surprises there?  I guess the ARMv4T is 
> also beyond patent expiration dates, no?
> 
> -- 
> 
> Rick C

Hi Rick,

The interrupt handling mechanism of ZAP is generic and the interrupt acknowledgement is implementation defined. Since Thumb has been around since at least 1994, I guess patents on it might have expired? 

Thanks,
Revanth 

Article: 160107
Subject: Re: ZAP : An open source ARM processor (feedback)
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 29 May 2017 07:40:48 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Monday, May 29, 2017 at 1:44:25 AM UTC-4, rickman wrote:
> ...I found a reddit page where you talk about patents and other things
> last December.  So I guess none of this is news to you.  :) ...

I would just like to state how damaging patents and intellectual property
rights are to the advancement of mankind.  They are nice for the private
advancement of a few, but they do not serve mankind well in any way,
shape, or form.  Even the incentive for profit they might bring for the
hard workers is not sufficient to override the loss to humanity when the
ability to learn and alter freely the cumulative knowledge of man is
suppressed by artificial means, such as by legal erections around otherwise
unencumbered concepts.

Patents, copyrights, and "intellectual property" rights are all evil,
of the devil, and serve to enslave us rather than free us.

Thank you,
Rick C. Hodgin

PS - Revanth, I only post this to address these systems.  I think your
     offering is not only fantastic, but exactly what we, as people,
     should be doing.  It is the best of us given over to others to
     then use as raw materials for their creation atop your prior work.
     Please allow me to say, "Thank you, Revanth," for your contribution
     to mankind.

Article: 160108
Subject: Re: ZAP : An open source ARM processor (feedback)
From: rickman <gnuarm@gmail.com>
Date: Tue, 30 May 2017 00:52:07 -0400
Links: << >>  << T >>  << A >>
Revanth Kamaraj wrote on 5/29/2017 10:20 AM:
> On Monday, May 29, 2017 at 11:14:25 AM UTC+5:30, rickman wrote:
>> revanth91kamaraj@gmail.com wrote on 5/28/2017 8:45 AM:
>>> Hi,
>>>
>>> I am the author of the Gihub project ZAP ( https://github.com/krevanth/ZAP ). It is a 10-stage pipelined ARMv4T compatible soft processor core with cache and memory management support. I developed it during my final semester in university.
>>>
>>> Would like your feedback/criticism of the project.
>>
>> I am curious.  Has this been up long?  I remember some years ago, maybe as
>> far back as 2002 ballpark, someone wrote code for an ARM7 I think.  He
>> posted the code on opencores if I recall correctly.  It was only up a month
>> or so and he received an invitation from ARM to discuss his code.  That
>> means he got a call from an ARM lawyer.  Seems there are parts of the ARM
>> architecture that are patented.  At that time it would have been very hard
>> to design around the patent.  I think it was related to interrupt
>> acknowledgement.
>>
>> Again, if I recall correctly, ARM asked him to remove his code, but included
>> a sweetener, they offered him a job!  So the code is gone.  I'm sorry I
>> never downloaded a copy, but it is unlikely I would have bothered to build
>> it, so no great loss.
>>
>> That particular patent may have expired.  But you can be sure there are
>> others that are still in force.  Otherwise, what would stop companies from
>> writing their own ARM processors and not paying ARM a royalty?
>>
>> I just looked up ARMv4T and that is the same instruction set as the ARM7T.
>> With a 10 stage pipeline I guess your design is more like the ARM9T.  If
>> this is the same instruction set, it must have the same interrupt
>> acknowledge design, no?  If the patent has expired you may be home free.
>>
>> Hmmm, while researching my facts for this I found a reddit page where you
>> talk about patents and other things last December.  So I guess none of this
>> is news to you.  :)   But that conversation was for the ARMv4 instruction
>> set, not the ARMv4T.  Any patent surprises there?  I guess the ARMv4T is
>> also beyond patent expiration dates, no?
>>
>> --
>>
>> Rick C
>
> Hi Rick,
>
> The interrupt handling mechanism of ZAP is generic and the interrupt acknowledgement is implementation defined. Since Thumb has been around since at least 1994, I guess patents on it might have expired?

I suppose.  That's why they have new designs that work better, faster, 
cheaper and have new patents.

So is your processor like the ARM9T?

-- 

Rick C

Article: 160109
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Tue, 30 May 2017 01:46:17 -0700 (PDT)
Links: << >>  << T >>  << A >>
The closest thing the design might resemble is an xscale machine by Intel.

Article: 160110
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Tue, 30 May 2017 01:53:21 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
> The closest thing the design might resemble is an xscale machine by Intel.

*partially, not as complex as XScale.

Article: 160111
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Tue, 30 May 2017 08:53:28 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Tuesday, May 30, 2017 at 2:23:24 PM UTC+5:30, Revanth Kamaraj wrote:
> On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
> > The closest thing the design might resemble is an xscale machine by Intel.
> 
> *partially, not as complex as XScale.

The project was done at my final semester in University (2016 MS(EE) grad). My intentions for ZAP are purely non commercial and academic. However, if this project might give me problems legally, is it wise to put it on Github as open source?

Regards,
Revanth.

Article: 160112
Subject: Re: ZAP : An open source ARM processor (feedback)
From: lasselangwadtchristensen@gmail.com
Date: Tue, 30 May 2017 09:23:18 -0700 (PDT)
Links: << >>  << T >>  << A >>
Den tirsdag den 30. maj 2017 kl. 17.53.36 UTC+2 skrev Revanth Kamaraj:
> On Tuesday, May 30, 2017 at 2:23:24 PM UTC+5:30, Revanth Kamaraj wrote:
> > On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
> > > The closest thing the design might resemble is an xscale machine by Intel.
> > 
> > *partially, not as complex as XScale.
> 
> The project was done at my final semester in University (2016 MS(EE) grad). My intentions for ZAP are purely non commercial and academic. However, if this project might give me problems legally, is it wise to put it on Github as open source?
> 

unless you got some secrets from ARM that you at not allowed to show others I 
don't see how it could get you in trouble

patents are not secrets




Article: 160113
Subject: Re: ZAP : An open source ARM processor (feedback)
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Tue, 30 May 2017 09:42:45 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Tuesday, May 30, 2017 at 12:23:25 PM UTC-4, lasselangwad...@gmail.com wrote:
> Den tirsdag den 30. maj 2017 kl. 17.53.36 UTC+2 skrev Revanth Kamaraj:
> > On Tuesday, May 30, 2017 at 2:23:24 PM UTC+5:30, Revanth Kamaraj wrote:
> > > On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
> > > > The closest thing the design might resemble is an xscale machine by Intel.
> > > 
> > > *partially, not as complex as XScale.
> > 
> > The project was done at my final semester in University (2016 MS(EE) grad). My intentions for ZAP are purely non commercial and academic. However, if this project might give me problems legally, is it wise to put it on Github as open source?
> > 
> 
> unless you got some secrets from ARM that you at not allowed to show others I 
> don't see how it could get you in trouble
> 
> patents are not secrets

Agree.  Worst case they'll ask you to take it down and prohibit you
from using those algorithms in future projects.

I'm very impressed by your work.

Thank you,
Rick C. Hodgin

Article: 160114
Subject: Re: ZAP : An open source ARM processor (feedback)
From: rickman <gnuarm@gmail.com>
Date: Tue, 30 May 2017 18:33:00 -0400
Links: << >>  << T >>  << A >>
Revanth Kamaraj wrote on 5/30/2017 11:53 AM:
> On Tuesday, May 30, 2017 at 2:23:24 PM UTC+5:30, Revanth Kamaraj wrote:
>> On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
>>> The closest thing the design might resemble is an xscale machine by Intel.
>>
>> *partially, not as complex as XScale.
>
> The project was done at my final semester in University (2016 MS(EE) grad). My intentions for ZAP are purely non commercial and academic. However, if this project might give me problems legally, is it wise to put it on Github as open source?

That's why I brought up the issue.  I don't think ARM is malevolent.  They 
are only interested in protecting their intellectual property.  As you point 
out their work is over 22 years old it is unlikely they have any current 
patents.  Since these are CPU designs that have been superseded by a number 
of newer designs, they likely have no more financial interest in them.

Wanna code up an ARM CM7?  ;)

-- 

Rick C

Article: 160115
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Revanth Kamaraj <revanth91kamaraj@gmail.com>
Date: Tue, 30 May 2017 20:59:23 -0700 (PDT)
Links: << >>  << T >>  << A >>
On Tuesday, May 30, 2017 at 10:12:48 PM UTC+5:30, Rick C. Hodgin wrote:
> On Tuesday, May 30, 2017 at 12:23:25 PM UTC-4, lasselangwad...@gmail.com wrote:
> > Den tirsdag den 30. maj 2017 kl. 17.53.36 UTC+2 skrev Revanth Kamaraj:
> > > On Tuesday, May 30, 2017 at 2:23:24 PM UTC+5:30, Revanth Kamaraj wrote:
> > > > On Tuesday, May 30, 2017 at 2:16:23 PM UTC+5:30, Revanth Kamaraj wrote:
> > > > > The closest thing the design might resemble is an xscale machine by Intel.
> > > > 
> > > > *partially, not as complex as XScale.
> > > 
> > > The project was done at my final semester in University (2016 MS(EE) grad). My intentions for ZAP are purely non commercial and academic. However, if this project might give me problems legally, is it wise to put it on Github as open source?
> > > 
> > 
> > unless you got some secrets from ARM that you at not allowed to show others I 
> > don't see how it could get you in trouble
> > 
> > patents are not secrets
> 
> Agree.  Worst case they'll ask you to take it down and prohibit you
> from using those algorithms in future projects.
> 
> I'm very impressed by your work.
> 
> Thank you,
> Rick C. Hodgin

Thanks.

Article: 160116
Subject: Re: ZAP : An open source ARM processor (feedback)
From: Richard Damon <Richard@Damon-Family.org>
Date: Wed, 31 May 2017 16:40:23 -0400
Links: << >>  << T >>  << A >>
On 5/29/17 10:40 AM, Rick C. Hodgin wrote:
> On Monday, May 29, 2017 at 1:44:25 AM UTC-4, rickman wrote:
>> ...I found a reddit page where you talk about patents and other things
>> last December.  So I guess none of this is news to you.  :) ...
> 
> I would just like to state how damaging patents and intellectual property
> rights are to the advancement of mankind.  They are nice for the private
> advancement of a few, but they do not serve mankind well in any way,
> shape, or form.  Even the incentive for profit they might bring for the
> hard workers is not sufficient to override the loss to humanity when the
> ability to learn and alter freely the cumulative knowledge of man is
> suppressed by artificial means, such as by legal erections around otherwise
> unencumbered concepts.
> 
> Patents, copyrights, and "intellectual property" rights are all evil,
> of the devil, and serve to enslave us rather than free us.
> 
> Thank you,
> Rick C. Hodgin
> 

Rick, as I have said before, if you truly believe this then your only 
real option is to cease IMMEDIATELY using anything covered by current IP 
restrictions (and that would include any open source products with 
restrictive licenses like the GNU licenses). Anything short is 
hypocrisy, which is sinful.

I realize this is basically impossible.

One key factor you refuse to acknowledge is that most of the resources 
you want to use only came about BECAUSE of the existing IP laws allow 
companies to be willing to spend money on research and development 
knowing that they will be able to earn money on the results.


Article: 160117
Subject: baud_generator (16x baud) used in UART transmitter logic
From: _Xilinx <feiphung27@gmail.com>
Date: Thu, 1 Jun 2017 05:30:42 -0700 (PDT)
Links: << >>  << T >>  << A >>
For http://www.ti.com/lit/ds/symlink/pc16550d.pdf#page=17 , how is the output of baud_generator (16x baud) used in transmitter logic ? 

I only see there is a transmitter timing control block in the functional block diagram, but I am not sure how it works exactly. Anyone ?

Article: 160118
Subject: Re: baud_generator (16x baud) used in UART transmitter logic
From: "Michael Kellett" <nospam@invalid.com>
Date: thu, 1 jun 2017 15:56:47 +0100
Links: << >>  << T >>  << A >>
_Xilinx:
> For http://www.ti.com/lit/ds/symlink/pc16550d.pdf#page=17 , how is the
output of baud_generator (16x baud) used in transmitter logic ? 
> 
> I only see there is a transmitter timing control block in the
functional block diagram, but I am not sure how it works exactly. Anyone
?

I think you'll need to Google about a bit on this one - the chip is old
enough for its insides to be public. 

Some how I don't think you are actually related to the Xilinx without  a
leading underscore so perhaps you should think of a more original handle
:-)

MK

Article: 160119
Subject: Re: baud_generator (16x baud) used in UART transmitter logic
From: rickman <gnuarm@gmail.com>
Date: Thu, 1 Jun 2017 12:41:58 -0400
Links: << >>  << T >>  << A >>
_Xilinx wrote on 6/1/2017 8:30 AM:
> For http://www.ti.com/lit/ds/symlink/pc16550d.pdf#page=17 , how is the output of baud_generator (16x baud) used in transmitter logic ?
>
> I only see there is a transmitter timing control block in the functional block diagram, but I am not sure how it works exactly. Anyone ?

The baud rate generator defines how fast the UART circuit works.  There are 
two ways of providing this control.  One is to generate a clock for the UART 
which goes to the clock input on each FF.  This is typically a square wave 
(or close to one).  The other is to generate an enable signal that lets the 
FFs in the UART to run from a master clock with actions disabled in the FFs 
on all cycles except for the ones enabled by the baud clock.  This means the 
enable must be active for only one clock of many.

-- 

Rick C

Article: 160120
Subject: Re: Test Driven Design?
From: Ilya Kalistru <stebanoid@gmail.com>
Date: Fri, 2 Jun 2017 15:54:01 -0700 (PDT)
Links: << >>  << T >>  << A >>
It's a draft of an article. 
https://docs.google.com/document/d/17LgQjxYdh8Dxy4NdFWWNYQ7up8MFNG4GQdPfv3s5LzI/edit?usp=sharing
It would be great if you left you comments right in the document or here, so that I could improve it.

Thanks.

Article: 160121
Subject: Article about using Non-Project Mode
From: Ilya Kalistru <stebanoid@gmail.com>
Date: Fri, 2 Jun 2017 15:55:39 -0700 (PDT)
Links: << >>  << T >>  << A >>
Hi!
During the discussion about "Test Driven Design?" I promised to write a paper about Non-Project Mode and how it helps with testing.
The problem is that I have never written any article. Moreover, English is not my native language.
I kindly ask you to review the article and help me to improve it. It is in Google docs and leaving comments right in the document is allowed. You also can comment it here if it is more convenient for you.
Thanks.

https://docs.google.com/document/d/17LgQjxYdh8Dxy4NdFWWNYQ7up8MFNG4GQdPfv3s5LzI/edit?usp=sharing

Article: 160122
Subject: Re: baud_generator (16x baud) used in UART transmitter logic
From: Gabor <nospam@nospam.com>
Date: Fri, 2 Jun 2017 21:33:44 -0400
Links: << >>  << T >>  << A >>
On Thursday, 6/1/2017 8:30 AM, _Xilinx wrote:
> For http://www.ti.com/lit/ds/symlink/pc16550d.pdf#page=17 , how is the output of baud_generator (16x baud) used in transmitter logic ?
> 
> I only see there is a transmitter timing control block in the functional block diagram, but I am not sure how it works exactly. Anyone ?
> 

It seems pretty obvious from the text.  You give the chip a clock up to
24 MHz.  Then there's a register that can divide that clock by any
whole number up to 65535.  The transmitter and receiver bit rate will
be 1/16th of the divided clock frequency.  For a simple UART, you only
need to be within about +/- 1% of nominal baud rate to work.  So if your
input clock is not a nice multiple of the desired baud rate it's best
if the clock is at least 800 times the desired rate.  If your intent
is to use this as a standard PC peripheral, your input clock should
match the input clock frequency used on PC motherboards.

Both transmit and receive sections of the UART run from the 16x clock
created by the baud rate generator.  For transmitting it may simply
use a free-running divide by 16 to generate the bit-rate clock.  For
the receiver, the sampling rate is 16x the baud rate.  Then the falling
edge of the start bit is used to reset a counter that creates the sample
time for subsequent bits (this is a simplified description).

If your intent is to re-create the guts of this chip in an FPGA, then
you can take rickman's suggestion of using a clock enable from the baud
rate generator rather than creating a clock.

-- 
Gabor

Article: 160123
Subject: Re: ZAP : An open source ARM processor (feedback)
From: rickman <gnuarm@gmail.com>
Date: Sat, 3 Jun 2017 01:24:01 -0400
Links: << >>  << T >>  << A >>
Richard Damon wrote on 6/2/2017 9:26 PM:

<<< Snipped a great deal of off topic crap >>>

> If you want to talk about this more, I suggest you can contact me off group,
> as this really isn't relevant to the newsgroup.


Why didn't you contact him directly off group rather than muddy up the place 
further?

-- 

Rick C

Article: 160124
Subject: Re: Article about using Non-Project Mode
From: Ilya Kalistru <stebanoid@gmail.com>
Date: Sat, 3 Jun 2017 01:24:44 -0700 (PDT)
Links: << >>  << T >>  << A >>
To comment a phrase in the document, you just select it and click "comment icon" which appears at the end if the line.



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