Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Meaning of port1 output can sink/source TTL input in 8051

Status
Not open for further replies.
L

louislu

Member level 1
Joined
Apr 5, 2004
Messages
40
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
426
some general knowledge

suddenly think of something...can someone clear my doubt...all regarding 8051 question...

1.what is the meaning of "port1 output can sink/source TTL input?i understand that when 1 are written to that port 1,they r pulled high by internal pull up...but y must be internal pulled up in order to use as input...n what is the meaning of source current when tat port 1 r externally pulled low

thanz
 

some general knowledge

At 8051 the ports don't have a "direction" register like other microcontrollers. If you write 1 at the port line it's the same as setting the port as output in high state or set as input (except port 0). The port have a weak pull up that will source current when it's pulled low by a external load like a resistor connected to ground or a transistor base and it works the same way either is input or output in high state. But the current capabilities are limited for the high state (limited at 4 LS TTL's inputs load) . When the output is set in low state can sink usually 20 mA trough an internal transistor.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top