"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
> In article <OJg*wmhMy@news.chiark.greenend.org.uk>,
> Theo <theom+news@chiark.greenend.org.uk> wrote:
> > The LFC1041 is a Ferranti part, so I suspect it's a custom logic chip
> > made for Lucas. The PDF I linked upthread has a block diagram. It
> > looks a bit like the Ferranti ULAs in 8-bit computers like the BBC
> > Micro, but that might only extend as far as the packaging. Ferranti did
> > make transistors and analogue chips too. So I suppose we can't rule out
> > some analogue stuff in there.
>
> Connectional logic with the SD1 lot is that the 4CU is entirely analogue.
> It can't be remapped in a conventional way. Those 4CUs used for racing etc
> were modified mainly by frigging the signal from the AFM. And of course
> larger injectors. The next Lucas generation - the 14CU - is digital and
> can be re-mapped using software.

According to the 4CU PDF upthread, U101 (the LFC1041AE) has various digital
functions:

RPM to digital converter
Digital Memory (fuel map)
Number-to-time counter
Voltage Controlled Oscillator (fuel trim)

and the input to the fuel map memory is 7 bits coming from an ADC in U102
(LFC1071AA). Apart from the ADC, U102 does look mostly analogue.

So it's digital, but it's not programmable. I assume the fuel map is
hardcoded in a ROM (of that vintage, to be programmable it would need a
quartz window for a UV-erasable EPROM) or maybe a PROM (writable one time
only).

Meanwhile the 14CU has a microprocessor in it, so it is programmable via
software in the modern sense.

Theo

In article <PJg*vXlMy@news.chiark.greenend.org.uk>,
Theo <theom+news@chiark.greenend.org.uk> wrote:
> "Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
> > In article <OJg*wmhMy@news.chiark.greenend.org.uk>,
> > Theo <theom+news@chiark.greenend.org.uk> wrote:
> > > The LFC1041 is a Ferranti part, so I suspect it's a custom logic chip
> > > made for Lucas. The PDF I linked upthread has a block diagram. It
> > > looks a bit like the Ferranti ULAs in 8-bit computers like the BBC
> > > Micro, but that might only extend as far as the packaging. Ferranti did
> > > make transistors and analogue chips too. So I suppose we can't rule out
> > > some analogue stuff in there.
> >
> > Connectional logic with the SD1 lot is that the 4CU is entirely analogue.
> > It can't be remapped in a conventional way. Those 4CUs used for racing etc
> > were modified mainly by frigging the signal from the AFM. And of course
> > larger injectors. The next Lucas generation - the 14CU - is digital and
> > can be re-mapped using software.

> According to the 4CU PDF upthread, U101 (the LFC1041AE) has various digital
> functions:

> RPM to digital converter
> Digital Memory (fuel map)
> Number-to-time counter
> Voltage Controlled Oscillator (fuel trim)

> and the input to the fuel map memory is 7 bits coming from an ADC in U102
> (LFC1071AA). Apart from the ADC, U102 does look mostly analogue.

> So it's digital, but it's not programmable. I assume the fuel map is
> hardcoded in a ROM (of that vintage, to be programmable it would need a
> quartz window for a UV-erasable EPROM) or maybe a PROM (writable one time
> only).

> Meanwhile the 14CU has a microprocessor in it, so it is programmable via
> software in the modern sense.

I've been in contact with the owner and he regards it as scrap. He's
currently using a Land Rover version from an engine with the same CR.
So I've changed U101 for one from a scrap Vitesse unit. No charge if he
tries it and not OK. But now have 5v Vcc.

--
*Who is this General Failure chap anyway - and why is he reading my HD? *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
> I've been in contact with the owner and he regards it as scrap. He's
> currently using a Land Rover version from an engine with the same CR.
> So I've changed U101 for one from a scrap Vitesse unit. No charge if he
> tries it and not OK. But now have 5v Vcc.

That's interesting. So it suggests U101 pin 11 was inhibiting the 5V rail.

Theo

On 23/04/2022 15:09, Theo wrote:
> "Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
>> I've been in contact with the owner and he regards it as scrap. He's
>> currently using a Land Rover version from an engine with the same CR.
>> So I've changed U101 for one from a scrap Vitesse unit. No charge if he
>> tries it and not OK. But now have 5v Vcc.
>
> That's interesting. So it suggests U101 pin 11 was inhibiting the 5V rail.

That seems a little incestuous.

While I thought pin 11 would stop the 5V rail from powering up, I
assumed that the U101 would have to be powered up and running to pull
the pin low, which seemed daft to turn it's own power off!

I guess the purpose may be a power-on style reset, that could be
slightly different to a reset via the reset pin. Or to remove power in
the case of some latch-up.