8051 Reset with membrane keypad

[mpm]

Have not tested it yet, but figured I would ask....

Can an 8051 be reset directly with a membrane type switch?
Specifically, the Atmel AT89S52 (but at some point the design /
availability could mandate some other 8051 derivative part, as yet
unknown.)

I plan to use a 4.7k / 1uF combination, and simply take Pin-9 high to
reset it.

For this particular type of project, I would normally use a uPC that
either has internal power-up reset on-chip, or maybe even an outboard
device like a DS1232 or something.

BUT, if it's acceptable to just use an non-debounced, unconditioned,
membrane switch to reset the uPC, this particular design could benefit
from the reduced parts count. Note that I would probably also use a
software watchdog, and I believe the AT89S52 has a power rail monitor
for brownout already built-in (which would also have been provided by
a DS1232 or equiv.)

What do you think?

 

[Eeyore]

Have not tested it yet, but figured I would ask....

Can an 8051 be reset directly with a membrane type switch?
Specifically, the Atmel AT89S52 (but at some point the design /
availability could mandate some other 8051 derivative part, as yet
unknown.)

I plan to use a 4.7k / 1uF combination, and simply take Pin-9 high to
reset it.

For this particular type of project, I would normally use a uPC that
either has internal power-up reset on-chip, or maybe even an outboard
device like a DS1232 or something.

BUT, if it's acceptable to just use an non-debounced, unconditioned,
membrane switch to reset the uPC, this particular design could benefit
from the reduced parts count. Note that I would probably also use a
software watchdog, and I believe the AT89S52 has a power rail monitor
for brownout already built-in (which would also have been provided by
a DS1232 or equiv.)

What do you think?

I think it's fine.

Include a low value resistor in series with the switch to limit the
discharge current from the cap.

1uF sounds a little low btw.

Graham

 

[Martin Riddle]

Have not tested it yet, but figured I would ask....

Can an 8051 be reset directly with a membrane type switch?
Specifically, the Atmel AT89S52 (but at some point the design /
availability could mandate some other 8051 derivative part, as yet
unknown.)

I plan to use a 4.7k / 1uF combination, and simply take Pin-9 high to
reset it.

For this particular type of project, I would normally use a uPC that
either has internal power-up reset on-chip, or maybe even an outboard
device like a DS1232 or something.

BUT, if it's acceptable to just use an non-debounced, unconditioned,
membrane switch to reset the uPC, this particular design could benefit
from the reduced parts count. Note that I would probably also use a
software watchdog, and I believe the AT89S52 has a power rail monitor
for brownout already built-in (which would also have been provided by
a DS1232 or equiv.)

What do you think?

Sounds like it will work, watch out for external noise that could reset it for you.
You could also use a software reset, jump to 0x0000.

Cheers