There was a NEC CPU upgrade kit, one used to replace the stock CPU, is this what you're talking about here? If so, I believe there was a battery that went with the chip. If the battery is dead the chip would not work. Or am I totally remember this wrong? b
On Sun, Nov 4, 2018 at 4:36 PM Ed C. via cctalk <cctalk@classiccmp.org> wrote: > Just had a look to this manual: > > http://www.bitsavers.org/pdf/dec/pdp11/pro3xx/EK-PC350-TM-001_Professional_300_Series_Technical_Manual_Dec82.pdf > > 5.2.3.4 Power-Up Self-Tests, this section mentions the existence of rom > containing basic power up tests. I assume you are not even getting there > and your system fails to execute from this rom and report any errors on > screen? > > In such case, A) is your cpu working? B) Is the rom code correct? > > > On Sun, Nov 4, 2018 at 10:11 PM Rob Jarratt <robert.jarr...@ntlworld.com> > wrote: > > > > > > > > -----Original Message----- > > > From: Eduardo Cruz [mailto:edcr...@gmail.com] > > > Sent: 04 November 2018 13:47 > > > To: r...@jarratt.me.uk; Rob Jarratt <robert.jarr...@ntlworld.com>; > > General > > > Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> > > > Cc: Tony Duell <ard.p850...@gmail.com> > > > Subject: Re: Datasheet for a NEC Chip in DEC Professional 350 > > > > > > A constant pulsing reset is usually a watchdog at play. Hardware > > watchdogs > > > are usually implemented in systems to reset everything should the > system > > > not meet one specific criteria: eg cpu touch one memory address before > X > > > amount of time, or pcb voltage lower than X volts, etc. > > > > > > Watchdogs are also usually found as software routines executed by the > cpu > > > also looking for specific conditions. These rarely issue a reset > hardware > > signal, > > > just restar the program. > > > > > > > It looks to me like the reset is every 10us. I don't know how long the > > watchdog is likely to be, the technical manual I have doesn't seem to > > mention it in the section on the reset logic. I am still trying to find > the > > source of the signal that seems to be in the "wrong" state. > > > > Regards > > > > Rob > > > > >
