Lcd For Z80-Driven Computers

EE JULY/AUGUST 1988 There is a growing tendency to use liquid-crystal displays (LCD) as the screen of computer monitors. Such dis- plays may also be used where the nor- mal monitor is too large or draws too much current; they are readily available. An LCD is normally driven by a micro- processor: in the proposed circuit by a Z80. The display in the proposed circuit is a Sharp Type LM16251: a full description of this appeared in the May 1986 issue of this magazine. It is located in the I/O region, addresses 0 to 3, of the pro- cessor. This arrangement enables the circuit also to be used in combination with the 32-bit I/O and timer cartridge described in the January 1987 issue of this magazine. This cartridge does not use the lowest four addresses (choose address 0 for the cartridge so that an ad- ditional I/O region of 0 to 15 is ob- tained). The address coding is effected by gates Ni to N4. When A2 to A7 are, and I0 REQ becomes low, the output of N3 goes low. If Ml is high (no int...