[sdiy] 7-segment LED displays with 4511 driver chip - max current?

MTG grant at musictechnologiesgroup.com
Thu Aug 6 00:39:27 CEST 2015


Oh gawd this new format ... I'm having a hard time figuring out who said 
what! ;-)

Anyway, that's really interesting about the PG300. I imagine the 
prototype on the developers bench had those attached for debugging 
maybe.  Or maybe they planned to use them but dropped it for price.

GB

> On Aug 5, 2015, at 1:29 PM, Rick Jansen <rick.jansen at xs4all.nl> wrote:
> I did not intend to imply that price was the most important consideration. I merely meant to give an example of an eighties product category where a 12 MHz (1 MIPS) processor (for one example) could handle the task and the designers decided that additional support chips were not necessary.
>
> What's really funny is that the product I'm talking about - the Roland PG-300 - actually has no 7-segment LED in the circuit, but if you examine the firmware, you'll find that they're calculating the BCD conversion for two 7-segment displays and driving the Port A outputs for LEDs that aren't even there. I think that shows it doesn't take much CPU power if it can be wasted like this.
>



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