Nat Semi SC/MP Low Cost Development System

[Realtime]

Excellent progress

Originally Posted by Phil__G

250 baud is well weird, has the crystal been changed?
I need to do some reading
"CL 0001" ?
...

Ohhhh…… I have 2 processor cards for the LCDS. A 4MHz SC/MP II and a 1MHz SC/MP. I’ve been using SC/MP II for testing as it’s less of a problem if it were to get damaged. But of course it runs twice the speed so that would explain the weird baud rate.
Will try the 1MHz card this evening.

CL 0001 is equivalent to PC 0001, which is shown at reset on the LCDS led display, (program counter). I take CL to mean current location but haven’t found an actual definition.

[Timbucus]

Cool - as P1 already points at 0x019B the Key Matrix I suspect that the index into the Matrix for display is done at 0x0118 by the ADI $25 which then uses E to get the contents and add one to address $0200 using the $65 offset off P1 as well instead of the expected -1(P2). Still struggling with the logic but, it seems related to counting the number of characters upto 9 to fill the display I think.

[SiriusHardware]

I'm still waiting to see how it can possibly be a useful teletype when it can only display 7-segment characters...

[Phil__G]

The SoC "Message" is a jolly fine example

[SiriusHardware]

Yes, but did you notice how 'Science Of Cambridge' got abbreviated to 'S-Of-C' because of that pesky 'm'....?

[Realtime]

According to John Miller-Kirkpatrick "NS have worked out a 40 character set which can be displayed using 7-seg plus a DP".

[Phil__G]

I wonder if it scrolls or just displays a static line of up to 9 characters?
If it scrolls long lines, "SoC-message-style" there must be a line buffer somewhere in RAM...
I expect it will just scroll 'live', ie character by character, at 110 baud it will be quite readable. For every new char received, shift the display left and write the new char on the right. It would be just like reading a 'real' teleprinter in real time, or like on the old TV sport results If only we had a Youtube of a Telekit in action...
The lack of delays suggests to me that its does async tx from the keypad and async rx to the display at the same time which is very clever

[Phil__G]

This is what we have so far:

[Timbucus]

My best guess at the display handler so far - working my way back up the code...

0110   02       CCL		; Ensure Carry is clear
0111   F4  40   ADI $40		; The character set starts at @ for 0x40
0113   94  02   JP +$02 	; goto $0117 and store the needed pattern for @A..Z[\]^_

0115   90  20   JMP +$20 	; to $0137

0117   02       CCL		; Ensure Carry is clear
0118   F4  25   ADI $25		; Character code in A is indexed into segment
011A   01       XAE		; display table at 01C0 using the offset register
011B   C1  80   LD E(P1)	; and the base of the data tables at 019C
011D   01       XAE		; Segments to light saved in E
011E   A9  65   ILD +$65(P1)	; Increment 0x0200 address (using P1 to get to RAM)
0120   01       XAE		; Segments tolight into A and location on display in E
0121   CA  80   ST E(P2)	; Store segments to light
0123   C4  0A   LDI $0A		; Have we run out of the 9 digits
0125   60       XRE		; (remember offset is in E)
0126   9C  0F   JNZ +$0F 	; if not goto $0137

0128   C2  01   LD +$01(P2)	; otherwise shift all 8 segments 1 to the left
012A   CE  01   ST @+$01(P2)
012C   B9  65   DLD +$65(P1)	; Remember P1 is used as base so 0x0200 is counter
012E   9C  F8   JNZ -$08 	; to $0128

0130   C4  01   LDI $01		; Reset P2 to the start of the display buffer
0132   32       XPAL P2		; increments above only affected lower byte
0133   C4  09   LDI $09		; Reset the number of characters to FULL 9
0135   C9  65   ST +$65(P1)	; at display counter

0137   C4  00   LDI $00		; A to zero
0139   CA  46   ST +$46(P2)	; zeros the value at $0247
013B   90  8F   JMP -$71 	; to $00CC (This is an XPPC)

[Phil__G]

Added as-yet-meaningless labels. I'm done for a while now

Except:

0111   F4  40   ADI $40		; The character set starts at @ for 0x40
0113   94  02   JP +$02 	; goto $0117 and store the needed pattern for @A..Z[\]^_
0115   90  20   JMP +$20 	; to $0137, exit without displaying
DISPLAY:

JP jump if positive ie if 7F or below its displayable, if 80h upward then return without displaying?

.

[circuitryboy]

I've been comparing the TELEKIT and Financier keypads, matching them up with the MM5762 schematic.
This is the ASCII lookup table with some H/W annotation and what the ASCII code becomes after that key has been 'shifted'.
(I haven't yet determined which key does the 'shifting')

[Realtime]

Originally Posted by Realtime

But of course it runs twice the speed so that would explain the weird baud rate.
Will try the 1MHz card this evening.

Indeed, with the SC/MP 1MHz module fitted the TTY output is 110 baud. Phew that's one less mystery. Still no change to the display on the TELEKIT though - just all segments on.

Very impressed at the rate of discovery and decoding of the TELEKIT EPROM

[Phil__G]

This had me baffled, at first it looked like SOUT states were being pushed off the edge of the world but looking at the barely-legible ETI diagram, the shift register is clocked by NRDS, so for every SIO instruction fetch theres a NRDS and so the SOUT state would be clocked into the shift register: (yes?)

0030   19       SIO                             ; Shift E out on SOUT
0031   19       SIO
0032   19       SIO
0033   19       SIO
0034   19       SIO
0035   19       SIO
0036   19       SIO
0037   19       SIO

in other words the SR is clocking all the time, every memory read, but its outputs dont change until Flag1 says so, and after these eight SIOs the SR will contain E. (?)
Then, as Ians comment says, Flag1 latches it, shifting continues internally but doesnt affect the latched SR outputs

0038   07       CAS    ; I believe this is resetting FLAG1 to disable shift register

[Realtime]

Now with a 110 baud input signal the FLAG0, FLAG1, SOUT and SIN signals are all active and periodic (FLAG1 seems to be same as FLAG0). The display more often than not get's cleared but no response from the keypad.The photo shows one bit of the TTY input, FLAG1 and SIN.
The TELEKIT is not resetting consistently at power up. It's a very slow rise time on NRST so I'm going to fit a lower value capacitor tomorrow. If that doesn't work then bolt on a reset circuit for now.

[Phil__G]

I like the DS1233, I use them a lot. Three wires, pos, neg & reset. A quid from RS

[Mark1960]

I’m not sure that figure 1 in the ETI article is the schematic for Telekit. I think it might be JMK’s proposal for addition to a second Introkit.

[circuitryboy]

Originally Posted by Mark1960

I’m not sure that figure 1 in the ETI article is the schematic for Telekit. I think it might be JMK’s proposal for addition to a second Introkit.

Exactly.
There's no way JM-K would have had access to a TELEKIT or its detailed circuit.
BYWOOD actually listed "SC/MP TTY kit (see ETI Sept 76)" in their ETI advert Oct & Nov '76.
Then it disappeared.

[Phil__G]

I'm not so sure. His proposal matches what we've found so far in the software and uses what appears to be identical techniques... at the time, well before Clive, wasnt he Nat Semis only serious potential customer in the UK, maybe they lent him a prototype?

[ortek_service]

Originally Posted by Realtime

>>
I expected there would be either a dedicated logic chip, designed for that purpose, or a SC/MP. Guess what?
Attachment 285444 Attachment 285445
Wow, a white ceramic SC/MP. That looks like the exact same keypad and flexi, so yes very interesting to see that repair on the VintageCalculators site.
>>

Yes, my Introkit also has a ceramic-packaged SC/MP (although a dark grey/red/brown, rather than White) Gold-top/pins one - Did they ever make the original PMOS SC/MP in a plastic-package, that the single-rail NMOS SC/MP-II always tends to be in?

Originally Posted by Realtime

>>
>>
I spent yesterday putting together a MM5204 to 2716 adapter so I can read back the EPROM on my DATAI/O 29B.
Attachment 285450

I'm going to put Phil_G's SC/MP Disassembler to good use once I've recovered the code and work out what the processor should be doing.

I'd also made an MM5204-to-2716 socket readout-adaptor for verifying the EPROM in my Introkit. It's nowhere near as compact and neat as your one looks, but I did knock it up in only an hour or to from a hand-sketch of interconnections required between datasheet printouts of their pinouts, by just patching lots of links with relatively-thick insulated TC-wire across some veroboard.

Although on mine, I schottky diode wire OR-ed the 5V supply from the programmer socket with an external +5V supply wire as I wanted to be able to switch both +5V and -12V supplies on at the same time, without upsetting the programmer, in case the EPROM didn't like only having one supply present. And didn't want to risk damaging it, before I'd read it. I also put some pull-down resistors on the Power-save & Program pins.

I was pleased it worked first-time when I tried it on a Dataman, and ChrisOddy also successfully used it to readout the Introkit's EPROM on one of his programmers and had been able to confirm code was identical to original SCIOS version.

[ortek_service]

Originally Posted by circuitryboy

Is it just me? I've been reading that second ETI page since it was in post #1, but I find the text in Fig.s 1 & 2
only 50% legible so didn't look for very long.
Of course it's exactly as given on Worldradiohistory.
I no longer have my hoard of old magazines. Does anyone have those pages on the original paper?
>>

Originally Posted by Timbucus

>>
I will hopefully be able to do a better scan of the pages on the weekend as I have a copy on the way... I had been looking out for one for a while due to the proto SCRUMPI mention.
>>
>>

I thought I would have an original copy of that issue, as I've got a nearly-complete set of ETI's all the way back to 1977, with around half of the issues back to 1972, as I'd been collecting back-issues of ETI's and many other Electronics magazines I'd missed at the time. So I could have re-scanned it. But annoyingly it seems I only have ETI Oct-Dec 1976 and 1976 ones before Sep'76.

And I don't tend to see ETI's (Although quite-common to see PE & PW / EE etc from that era) that old at Radio Rallies very often. Although 1980's ETI's ones are fairly-common and I've got quite a few duplicates of those (especially after ChrisOddy gave me all of his in Binders back to 1980 - When I first stated buying EE and my Brother HE / a friend buying ETI).

However, whilst looking through some of mine, I did notice that ETI Sep 1978 (I'd originally thought the blurred text on it said) issue has a review of the recently-launched MK14.