CSCI 255, ENGR 274, ECE 212 -- 28 September, 2000
Announcements
MSI-like components
CMOS transmission gates
Open-collector gates
"In general, open-collector gates and tri-state gates are used for
the same kinds of functions. But tri-states are more economical because
they do not require the external resistor. They have largely replaced
open-colector gates in modern designs." -- textbook, p. 210
Tri-state devices
- 0
- 1
- Z -- high impedance state
- typical configuration include
- m data inputs
- one control input
- m data outputs
- typical chips include
Read-only memories (ROM)
- n address inputs
- m data outputs
- data is organized in words
- 2n×m bits
Writing the ROM
Little ROMs to big ROMs