1. ACOE2551 Microprocessors Common TTL Devices used in Microprocessor Systems

2. ACOE2552 Decoders Dual 2-to-4 Decoder (74XX139)3-to-8 Decoder (74XX138)

3. ACOE2553 Buffers Octal Buffer (74XX244)Octal Bidirectional Buffer (74XX245) If E1 = 0 then Y (3..0) = I (3..0) else Y (3..0) = Hi-Z (i.e Open) If E2 = 0 then Y (7..4) = I (7..4) else Y (7..4) = Hi-Z (i.e Open) If G = 1 then A (7..0) = Hi-Z and B (7..0) = Hi-Z else (if G = 0) and DIR = 0 then A (7..0) = B (7..0) else (if G = 0) and DIR = 1 then B (7..0) = A (7..0)

4. ACOE2554 Latches Octal Latch (74XX373, 74XX573) If E = 1 then the data at the D inputs [D (7..0) ] is latched into the flip-flops. If E = 0 then the outputs of the flip-flops do not change, irrespective of the data at the D inputs [D (7..0) ]. If OE = 0 then the outputs of the flip-flops appear at the Q (7..0) outputs, else Q (7..0) = Hi-Z (i.e Open)

5. ACOE2555 Octal Buffers