Testing a 1488 line driver...
geneb at deltasoft.com
Wed Jan 2 21:10:29 CST 2008
I've got an Ampro Littleboard that I'm trying to bring back to life.
Sometime last year it quit transmitting data on Port A (the console port)
so I shelved it until I had time to look at it.
I've checked the Z-80 DART with a logic probe and I'm seeing data coming
out of Port A (Pin 15 on the DART) when the machine boots up. I check the
input pin on the 1488, and get the same sound (the logic probe chirps with
each state transition) as I get out of the DART. However, checking the
output of the 1488, I don't get anything. Since I don't want to blow my
probe apart on 12V, I used an LED to watch the output on the 1488. The
LED lights the instant I attach it to the output and doesn't flicker or go
out when I reboot the computer to make it send data out the port.
The Port should be running at 9600 baud, so I should see at least some
flicker activity on the LED if the 1488 is toggling the output pin.
Before I spend the time to replace the 1488, I'd like to hear from you
folks if the chip is actually bad. Is what I'm seeing indicative of a
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
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