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The Compact Computer 40 (CC40)


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#201 acadiel OFFLINE  

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Posted Wed Nov 8, 2017 12:12 PM

Circling back around to the cartridge again.  Brain - do you have an updated diagram of what you need from me for traces, etc?

 

Thanks!



#202 brain OFFLINE  

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Posted Wed Nov 8, 2017 12:38 PM

Circling back around to the cartridge again.  Brain - do you have an updated diagram of what you need from me for traces, etc?

 

Thanks!

Yep:

  • Should I flip the naming of the pins in your readout?
  • For items like the diode and resistors, what is the other side connected to?
  • Can you verify that PIN35 of cc40 alone connects to the !CS line?  It seems strange that CRAM connects to the !CS line but !CROM does not. (or if it does, it connects through the resistor.  I would expect both CRAM and CROM to be configured the same.

 

Jim



#203 brain OFFLINE  

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Posted Wed Nov 8, 2017 8:36 PM

Also, what is the actual thickness of the PCB?  1.6mm FF4 does not fit, so need to know the actual thickness.



#204 acadiel OFFLINE  

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Posted Thu Nov 9, 2017 4:27 PM

Also, what is the actual thickness of the PCB?  1.6mm FF4 does not fit, so need to know the actual thickness.


Micrometer pic attached. :)

41e9192f65e6ed0dec756c507e38e2ce.jpg

#205 acadiel OFFLINE  

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Posted Thu Nov 9, 2017 4:58 PM

Looking at the picture (attached below), from my reference point: 

  • Fingers 1-20 are on the top of the board (bottom to top)
  • Fingers 21-40 are on the bottom of the board (top to bottom)
  • Pin 1 of the PROM is the A14 pin (top left)
  • Pin 28 of the PROM is D3 (bottom right)
  • Finger 20 (VCC) goes to Diode (1) left side, out past  Resistor (2), which then goes to pin PROM pin 15 (VCC).  
  • Finger 21 (!CROM?) goes into Resistor (2) and out to PROM pin 15 (VCC)
  • Finger 27 (GND) goes to the - Battery, then to the top right resistor, then to PROM pin 14 (GND)
  • Finger 35 (!CRAM?) goes to PROM pin 23 (!CS), then to resistor 2 (where you have it labeled CROM)
  • Finger 39 (!WE?) goes to the left side of the bottom resistor (above A13 on the PROM), and the output from that resistor goes to PROM pin #2 (A12), and is also jumpered to the left solder pad under that bottom most resistor (left side).
  • The second diode (hooked to VBATT) is simply there to keep voltage from backfeeding into VCC, looks like.

 

Does this help?

PIN	EPROM	SIGNAL
1	PIN14	GND
2	N/C	N/C
3	N/C	N/C
4	PIN19	A9
5	PIN20	A11
6	PIN21	!OE
7	N/C	N/C
8	N/C	N/C
9	N/C	N/C
10	N/C	N/C
11	N/C	N/C
12	PIN1	A14
13	N/C	N/C
14	PIN28	D3
15	PIN9	A1
16	PIN7	A3
17	N/C	N/C
18	PIN2	A12
19	PIN3	A7
20	VCC	DIODE1
21	!CROM	RESISTOR2
22	PIN4	A6
23	PIN5	A5
24	PIN6	A4
25	PIN8	A2
26	PIN10	A0
27	BATT-	GND
28	PIN13	D2
29	PIN12	D1
30	PIN11	D0
31	PIN25	D6
32	PIN26	D5
33	PIN27	D4
34	PIN24	D7
35	PIN23	!CRAM
36	PIN22	A10
37	PIN18	A8
38	N/C	N/C
39	PIN16	!WE
40	PIN17	A13

Attached Files



#206 brain OFFLINE  

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Posted Thu Nov 9, 2017 7:43 PM

Notes:

 

  • Two previously unknown signals (!OE and !WE) are now known
  • top diode is to prevent battery from feeding cc40. 
  • Bottom diode is to prevent cc40 from trying to power battery
  • On your note for pin39 (!WE), can you provide more clarity?  As I am looking at the pics, it looks like pin 39 goes to !WE on the PROM, then it goes up to a pad right above it and below the resistor pad.  That pad does not look connected to the resistor pad right above it.  The other side of that resistor looks to be connected to the pad right below it, and both traces look to be connected to PROM A11.  The left side of that resistor looks to go up to the top of the IC and then udner it (I assume to the pin 2 (A12) you mention.

Questions

 

  • Regardless of the question around !WE, having a resistor from A11 to A12 makes no sense.  It must be some vestige of the cart's previous use.
  • The top right battery connects something to battery ground, but the other side weaves along the right side and then disappears under the IC.  Any idea where it goes?
  • The 1mm caliper reading is much appreciated, but the board hosue is asking if it is .8mm, .9mm, 1mm, 1.1mm, or 1.2mm.  Anyone with a digital caliper who can provide more precision?

Without the top right resistor in the schematic yet, and assuming the bottom resistor is unneeded, here is the PCB (I kept the bank switches, so you can battery back up 16 banks of 32kB):

Attached Files


Edited by brain, Thu Nov 9, 2017 7:45 PM.


#207 acadiel OFFLINE  

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Posted Sun Nov 12, 2017 9:06 PM

I'll get back to the board in the next day or two and get you the answers you are looking for Jim :)



#208 brain OFFLINE  

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Posted Sun Nov 12, 2017 10:51 PM

OK, thanks.  I'll hold off on sending the board order in until I hear back.

 

Jim



#209 acadiel OFFLINE  

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Posted Mon Nov 13, 2017 7:49 AM

Notes:

 

  • Two previously unknown signals (!OE and !WE) are now known
  • top diode is to prevent battery from feeding cc40. 
  • Bottom diode is to prevent cc40 from trying to power battery
  • On your note for pin39 (!WE), can you provide more clarity?  As I am looking at the pics, it looks like pin 39 goes to !WE on the PROM, then it goes up to a pad right above it and below the resistor pad.  That pad does not look connected to the resistor pad right above it.  The other side of that resistor looks to be connected to the pad right below it, and both traces look to be connected to PROM A11.  The left side of that resistor looks to go up to the top of the IC and then udner it (I assume to the pin 2 (A12) you mention.

Questions

 

  • Regardless of the question around !WE, having a resistor from A11 to A12 makes no sense.  It must be some vestige of the cart's previous use.
  • The top right battery connects something to battery ground, but the other side weaves along the right side and then disappears under the IC.  Any idea where it goes?
  • The 1mm caliper reading is much appreciated, but the board hosue is asking if it is .8mm, .9mm, 1mm, 1.1mm, or 1.2mm.  Anyone with a digital caliper who can provide more precision?

Without the top right resistor in the schematic yet, and assuming the bottom resistor is unneeded, here is the PCB (I kept the bank switches, so you can battery back up 16 banks of 32kB):

 

Answers: 

 

* Finger 39 !WE does indeed go to the jumper under the top of the board that is under the top/middle of the RAM with a VIA.  Once on top, it does go to !WE on the RAM.  Then to an empty trace right about A13 on the RAMwith a VIA.  All I can think is that unpopulated component (Resistor or diode) was for some other use.  (This was an error on my part.)

* No resistor on from A11 to A12.  A11 has a resistor from finger to RAM.  Doesn't appear to be connected in any way to A12.

* The battery VIA for negative goes under and over to RGND (top right resistor)

* The 1mm reading is the best I can do for thickness.  I don't have a digital micrometer. :(

 

Does this clarify everything?  

 

edit: I'm going to take a few mins and double trace the three resistors for you just to make sure.

 

edit 2: 

top right resistor, RGND from battery and other side to GND finger and GND on RAM

middle resistor:  VCC on RAM and other side to finger 21 (CROM).  Intentionally Broken trace that goes to A13 on RAM (probably different RAM chip)

bottom resistor: PIN 20 (A11) on RAM and other side to via underneath that travels directly left.  This via then goes underneath the IC to another underneath the RAM right below VCC.  It then travels to the rightmost of two VIAs that is underneath the RAM still, but right below D5 (two dots near each other).  This via then goes back on top, and exits the right side of the RAM near the fingers and goes to A11 (Finger 5)

 

Thanks for your hard work!



#210 brain OFFLINE  

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Posted Mon Nov 13, 2017 6:32 PM

OK, one more question and I believe I have the unit mapped out.

 

GND (pin1) is connected to the resistor (6.8K, from what I can tell) at top of board, and that connects to battery ground.  It also connects to a ground on the connector (pin 27).  That seems to indicate pin 1 is not the same ground as pin 27.  Can you verify if those two pins are connected in some other way, or, when inserted in the unit, those two pins are shorted both to ground?

 

JIm



#211 acadiel OFFLINE  

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Posted Tue Nov 14, 2017 10:47 AM

Those two grounds are tied together, kinda.

 

Finger 27 goes to the bottom of the PCB to the battery connector.

 

Finger 1 on top of the PCB goes under the RAM IC.  I don't know where it goes from there (I can't see).  However, it has continuity with pin #14 of the RAM IC, perhaps via that third VIA immediately left of the D3 finger (which isn't labeled in your diagram).  That via goes under, above, under, and then to the right side of the resistor on the top right.  Then, of course, the left side of the resistor goes to the battery ground on top, and on the bottom, the battery ground goes to Finger 27.

 

That help?



#212 speccery OFFLINE  

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Posted Tue Nov 14, 2017 11:09 AM

I apologise in advance by asking a few potentially off topic questions - but partially because of this very thread (that I found very interesting although didn't have the time to read through carefully) I became interested in the CC40 and TI-74 and I acquired a TI-74. Now being a proud owner of that, I have a couple of questions. Sorry if these are stupid:

  • Is the Basic language manual available somewhere online?
  • Does the Basic support machine code programming somehow? Other than replacing the system ROM chip...

I saw both the CC40 and TI-74 in the TI Treff in Italy and couldn't help myself - had to get one of them  :)



#213 OLD CS1 OFFLINE  

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Posted Tue Nov 14, 2017 11:32 AM

@speccery: Have a look here.



#214 acadiel OFFLINE  

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Posted Tue Nov 14, 2017 11:37 AM

The 74 has a different cartridge than the CC-40.  It's also a female cartridge, which means we'd have to really scratch our heads to figure out where to get the cart connector from :)

 

Earlier in the thread, I was wondering if we could solder the 32K RAM chip to the 74's RAM chip (plus the extra lines) and make a simple disable switch if we choose to use the cart port's address space instead of the RAM chip.  I'd need someone to help me out with that, though about what to hook up where.  D0-D8 and the address lines that hook up to the 8K RAM chip are easy enough.  It's where to hook the remaining wires (A13 and A14 and the remaining pins, and any 'selection' type stuff.)



#215 brain OFFLINE  

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Posted Tue Nov 14, 2017 5:02 PM

Those two grounds are tied together, kinda.

 

Finger 27 goes to the bottom of the PCB to the battery connector.

 

Finger 1 on top of the PCB goes under the RAM IC.  I don't know where it goes from there (I can't see).  However, it has continuity with pin #14 of the RAM IC, perhaps via that third VIA immediately left of the D3 finger (which isn't labeled in your diagram).  That via goes under, above, under, and then to the right side of the resistor on the top right.  Then, of course, the left side of the resistor goes to the battery ground on top, and on the bottom, the battery ground goes to Finger 27.

 

That help?

That's bizarre.

 

I can only image it allows the battery to sit in between the 0 and +5 rails of the RAM IC, as it would elevate the RAM ground above battery ground when the unit was pulled from the cc40, but it's unclear to me how that works.

 

Can you measure the resistors?  I calculate the top right one as 6k8, and the other as 3K3, but no clue on the third, and want to check my numbers.

 

Here are some updated pics:

Attached Files


Edited by brain, Tue Nov 14, 2017 5:03 PM.


#216 acadiel OFFLINE  

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Posted Tue Nov 14, 2017 8:00 PM

That's bizarre.

 

I can only image it allows the battery to sit in between the 0 and +5 rails of the RAM IC, as it would elevate the RAM ground above battery ground when the unit was pulled from the cc40, but it's unclear to me how that works.

 

Can you measure the resistors?  I calculate the top right one as 6k8, and the other as 3K3, but no clue on the third, and want to check my numbers.

 

Here are some updated pics:

 

Top right resistor:  6.8K confirmed.

Middle resistor: 3.3K confirmed.

Bottom resistor: appears to be 4.7 ohms.  yellow, violet, gold gold.  Rings up as 4.9 and sometimes 4.8.






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