4 Jun
2010
4 Jun
'10
11:04 a.m.
Have a Data I/O System 19 programmer for about 10 years and use it
quite frequently to program old bipolar PROMs which newer programmers
can't handle, anyway a week ago it powers up with a constant beep and
and all the lights turn on, any ideas what could be wrong? Is there
something that normally goes on these units?
I have never worked on (or even seen) one of these units, but I've seen
simialr symptoms on otehr devices. if the LEDs and beeper are driven by a
TTL latch (say a '273), it would be logical to make the drive lines
active low (LED from output to Vcc), since TTL can sink more than it can
source. At which point, all LEDs become active when the latch is reset,
and are only turned off when the latch is written to by the
mircoprocessor system
So if the microprocessor isn't doing the right things (CPU, ROm, RAM,
support logic failuire), then the latch will never be written to. Hence
the 'all lights on and beep'.
-tony