I want to build an AB 1771 trainer

[Ron Beaufort]

Greetings, JorgeR,

you said:

You send a BCD number as one four bit signal per decimal digit and each time you enter it using the strobe bit?

I really think you have the idea ... but let's change your statement just a little bit for clarity:

You send a BCD number as one four bit signal per decimal digit and each time you tell the display unit to "record it" by pulsing the appropriate strobe bit.

Actually you have four strobe bits ... one bit for each digit on the display. The advantage to this system is that you get to REUSE the same four "digit bits" for each individual digit. Without this method you'd need a total of 16 bits (four bits for each digit). But with this method you only need 8 bits (four bits for ALL of the digits - and four strobe bits).

Of course this all assumes that you're using a four digit display.

As for the displays used on most "trainers" ... all of the ones that I've ever seen DO have strobe lines ... but the instructors seldom require that the students use them ... there is quite a bit of time-consuming "full-contact" programming involved in making them work correctly ... most beginning students find the exercise to be quite challenging ... don't get me wrong - there is a LOT to be learned from the exercise ... BUT ... I haven't used it for my students in years since BCD displays don't seem to be as popular as they used to be ... most integrators have switched over to using things like PanelViews for their operator interfaces ... personally, I think the lab time required to program a BCD display could be put to better use ... still if a guy has one available to tinker around with at home, this would be an EXCELLENT way to learn some valuable concepts ...