27 Oct
2010
27 Oct
'10
9:13 p.m.
On 2010 Oct 27, at 5:07 PM, Chuck Guzis wrote:
On 28 Oct 2010 at 0:26, John Honniball wrote:
.. they also differ from straight ROMS in their drive capabilities of
course.
The 68 and 74 have constant-current drivers for LEDs.
Then there was National's oddball inverse-function IC: 7-segment input
converted to BCD out.
On the subject of binary to hex 7-segment
decoders, has anyone
ever seen a DM9368? ISTR that it's a pre-programmed PROM of
some kind, taking in four bits of binary (plus some ripple
blanking pins) and outputting 7-segment drive signals for
0-9 and A-F.
No, there's a latch in there also. As I mentioned yesterday, it's
part of the Fairchild 9368/9370/9374 series As a pure ROM, you may be thinking of the MC4039,
which, by
Motorola's admission, was nothing but a preprogrammed version of the
XC170 128-bit mask ROM. Circa 1969.
The same ROM was used as the MC4001 BCD-to-Binary/Binary-to-BCD
encoder.