From: Nicolas Welte (welte_at_chemie.uni-konstanz.de)
Date: 2002-06-27 12:58:00
Hi,
I just got my 14 day free trial access to freetradezone, now I can download
all the datasheets for obsolete components for free again. If someone has
some ideas what I should download, just let me know :-)
The only datasheet I needed was the NEC uPD445 1k x 4 static RAM chip, which
looks a lot like a 6550 (from the PET 2001) because it has the same oversized
DIL package, but with only 20 pins. I found a few of them in the trash, and
immediately thought I could use them as a better 6550 replacement than the
2114.
The pinout is (just for the records):
uPD445
+---\/---+
1 -|a3 Vcc|- 20
2 -|a2 a4|- 19
3 -|a1 r/w|- 18
4 -|a0 /ce1|- 17
5 -|a5 od|- 16
6 -|a6 ce2|- 15
7 -|a7 a8|- 14
8 -|gnd a9|- 13
9 -|io1 io4|- 12
10 -|io2 io3|- 11
+--------+
od is output disable and must be 0 for normal operation. It is not an
additional chip select. Access times are 650ns for the standard device (L)
and 450ns for the device with L-1 suffix.
Nicolas
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