Using a 27C256 ROM to drive a set of 7 segment displays from an 8 bit register
Inputs:
- A7..A0: Register input
- A9..A8: Digit multiplex select
- A11..A10: Decode mode select
- A12: Leading zero blank
- A13: Zero blank chain in
- A14: Common Anode/Cathode select
Outputs:
- D6..D0: G,F,E,D,C,B,A
- D7: Zero blank chain out
Decode mode:
- 00: Unsigned 8 bit decimal (requires 3 digits)
- 01: Signed 8 bit decimal (requires 4 digits)
- 10: Hexadecimal (requires 2 digits)
- 11: Code B (2 digit, BCD plus -,E,H,L,P)