8051 microcontroller external bus interface circuit, the realization of external register operation,
(1) low 8 address reuse, with 8 bit data bus by the ALE signal to distinguish the address;
(2) external register address 0 x3f0-0 x3ff space;
(3) the design of asynchronous clock and MCU interface signals, frequency of MCU clock 4 times
Bosses RTL circuit diagram is given, be urgent!