In Motorola multiplexed-bus mode this pin is DS, an active high input which works with CS to enable read and write operation. In Intel/ National multiplexed-bus mode this pin is RD, an active low input which enables a read-cycle and configures the data bus lines (AD0-AD7) as outputs. 4 44 AS/ALE Address Strobe / Address Latch Enable (Input). Falling edge is used to sample address into the Address Latch circuit. 5 45 CS Chip Select (Input). Active low input enabling a microprocessor read or write