??? 02/16/05 13:52 Read: times |
#87646 - wire wrap and breadboards Responding to: ???'s previous message |
Wire wrap and breadboards severely limit what you can use of modern chips. It is a common misconception that it is the clock speed that has to be watched - WRONG, it is the risetimes and the power. I am not looking at a datasheet, so the numbers are approximate from memory:
a 74ALS raise 40mA in 2ns a 74HC rasie 1 mA in 10ns you figure. Also when breadboarding/wirewrapping do not use processors with a Max clock speed above 12 MHX YES a max speed - again the clock does not matter but the max speed indicates the risetimes of the chip. NOW here is a problem: the chips are specified as capable of a max speed of .. NOTHING forbid a mnufacturere from substituting a faster chip and label it the same (NOTE there are never any minimum rise times listed) so you may do everything right (supposedly slow uC, supposedly slow chips) and still get in trouble with your breadboard/wire wrap. My suggestion: Buy a 'protoboard" all will be well and you can tap the port signals off the protoboard to your breadboard (if needed round the pulses with some small RC circuits). Erik |
Topic | Author | Date |
Problem getting 8051 chip to work | 01/01/70 00:00 | |
tie ~EA pin to Vcc | 01/01/70 00:00 | |
tie Vpp/~EA pin to Vcc | 01/01/70 00:00 | |
to connect or not? | 01/01/70 00:00 | |
conbnect | 01/01/70 00:00 | |
If it helps.... | 01/01/70 00:00 | |
Reset Capacitor | 01/01/70 00:00 | |
connect | 01/01/70 00:00 | |
T89C51RD2 | 01/01/70 00:00 | |
This device is ISP | 01/01/70 00:00 | |
VCC and GND? | 01/01/70 00:00 | |
I think you do not load | 01/01/70 00:00 | |
Series resistor for LED? | 01/01/70 00:00 | |
74F14 | 01/01/70 00:00 | |
give me +1 too | 01/01/70 00:00 | |
done | 01/01/70 00:00 | |
Sorry | 01/01/70 00:00 | |
LED Polarity | 01/01/70 00:00 | |
Does not seem to be the cause | 01/01/70 00:00 | |
Ouch! | 01/01/70 00:00 | |
FAST-TTL and breadboarded design | 01/01/70 00:00 | |
Ground bounce | 01/01/70 00:00 | |
Bad news 74F =( | 01/01/70 00:00 | |
HCT? | 01/01/70 00:00 | |
LS, HCT and maybe AHCT | 01/01/70 00:00 | |
Got it | 01/01/70 00:00 | |
wire wrap and breadboards | 01/01/70 00:00 | |
I use protoboard | 01/01/70 00:00 | |
the problem with that is | 01/01/70 00:00 | |
Thanks | 01/01/70 00:00 | |
Why do you want to use 74F chips? | 01/01/70 00:00 | |
well...![]() | 01/01/70 00:00 | |
maybe you are still in ISP mode? | 01/01/70 00:00 | |
1st things 1st please | 01/01/70 00:00 | |
Thanks | 01/01/70 00:00 | |
bounce on non PCB | 01/01/70 00:00 | |
Analytical thinking | 01/01/70 00:00 |