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FarmerPotato

Geneve Clock Chip MM58274 source?

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2 hours ago, mizapf said:

 

Preventing direct access to hardware is one of the reasons why the privileged mode was invented for processors. This could be done on the TMS99105 since it has such a mode. You cannot restrict the address access, but you could use a CRU bit to guard the clock hardware, and the TMS99105 allows access to CRU addresses 1C00 and higher only in privileged mode.

Yes, but it's still tricky to apply the tools to the problem at hand. Like you said, 99105 does not have "protected memory" features (The TM 990s with map feature with LMF instruction sort of do.)

 

I am going to place all of MDOS in user mode. (So the supervisor is invoked anytime MDOS does an XOP or there is an interrupt.) 

 

But it's MDOS itself reading and writing the clock. For instance to implement the DATE command, the XOPs for get/set date time, etc.

 

To present a hardware abstraction layer, the memory mapper (in the FPGA) would have to act when it sees certain addresses in certain modes.

 

I could do that... I've thought it all through. Some ways are:

 

1. Implement page faulting for certain mode bits+addresses. Raise INT2 for page fault. Handle faults in software. Really gross--essentially you have to decode the offending instruction to implement it.

 

2. Put a big ball of FPGA glue on those addresses, which synthesizes the expected read/write behavior at F130-F14F ports. If I'm doing that, I might as well use any clock chip behind the glue. 

 

3. I would prefer to use real chips, and just attach the MM58174 clock chip to the expected memory-mapped ports. These would be F130-F13F when MDOS mode is active.

The FPGA would barely get involved. It just  outputs the page register value to the bus like any other memory cycle. 

 

So my need is still to understand in detail what those clock memory-mapped ports are in MDOS mode. Why they seem to be read at F130-F13E but written at F130-F14E. And why I see MDOS write F13E as both the clock settings register CKSTRG and a data register.

 

 

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I found some MM58174 clock chips for $0.75

 

The only difference vs the MM58274 that is the Geneve 9640, is that '174 does not have tens of years.

 

So it could be used, but with the tens-of-years register hard-wired to return '2'. It would be accurate
until 2030! And that's pretty far away!

 

On the other hand, Microchip MCP795W10 is $1.50, has SPI interface, and the FPGA memory-mapper could simulate the 58274
interface to it. To ensure compatibility.

 

MCP795W10 has the needed features, plus hundredths of seconds and year to 2399. Battery-backed SRAM, and helpfully records
when the power failed or came back on. Has a watchdog timer, two alarms, two external counters, square wave generator, 128 bytes EEPROM.
 

I'm inclined to use MCP795W10 or similar, connected to the memory mapper. So compatibility comes with a ball of FPGA glue, with wait states if needed.

 

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You might also want to check here for the MM58274. One vendor on the list says they have nine of them and the other says they have one. Only the one with one lists a price ($26). Both are reliable vendors.

 

Of course, this one says they have 26,000 of them, but they are a Chinese source that sometimes plays a bit fast with their products. When they're good, they're really good, but when they're bad, the product is abysmal. I've bought a few things from them in the past and the results were mixed, so I've tended to avoid them unless they were one of the primary remaining sources for the item.

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17 hours ago, Ksarul said:

You might also want to check here for the MM58274. One vendor on the list says they have nine of them and the other says they have one. Only the one with one lists a price ($26). Both are reliable vendors.

 

Of course, this one says they have 26,000 of them, but they are a Chinese source that sometimes plays a bit fast with their products. When they're good, they're really good, but when they're bad, the product is abysmal. I've bought a few things from them in the past and the results were mixed, so I've tended to avoid them unless they were one of the primary remaining sources for the item.

 

Yeah, I found utsource.com a while back.  It appears to go to Shenzhen and HK marketplace vendors, not their own stuff. I have worked with two on alibaba.com (who have sent me working 4464, 99105 and 9958). Polida2008 (eBay) has been good so far--Polida is part of a similar company.  

I've RFQed on utsource.com for some  thinly listed stuff and got a "sorry, we have no stock". 

 

I think the MM58274 is out of the running. Even at $7 it would be a bad choice. I'd rather go to the effort to make a memory-mapped interface around a $1.50 chip, that is still in production.

 

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On 11/9/2020 at 7:33 PM, FarmerPotato said:

The MM58167 has several interesting features that the '274 does not. However, it's not register-compatible AND it has no years (why?)

The clock I designed myself, for my TI 99/4A, uses the MM58167. Back then, that one had thousands of a second. There was some other type (don't remember the number) that had years, but only full seconds. I wanted the resolution.

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2 hours ago, apersson850 said:

The clock I designed myself, for my TI 99/4A, uses the MM58167. Back then, that one had thousands of a second. There was some other type (don't remember the number) that had years, but only full seconds. I wanted the resolution.

I like the MM58167 for that reason, too. 

 

Microchip has 0.01s.  For my first TI digital watch, I picked the one that had 0.01s on stopwatch. Used the .01 as a random number generator, instead of dice!

 

Details are here, for each chip I have compared:

https://docs.google.com/spreadsheets/d/1LGUA2ZyWv_TxHcGTVgS_4XnP801m3evRI5krbs0MbAg/edit?usp=sharing

 

I think the Microchip has a programmable oscillator output, which you can connect to the event counter input, so you could have your own adjustable timer.

 

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