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Microprocessors. Common TTL Devices used in Microprocessor Systems. 3-to-8 Decoder (74XX138). Decoders. Dual 2-to-4 Decoder (74XX139). Octal Bidirectional Buffer (74XX245). Buffers. Octal Buffer (74XX244). If G = 1 then A (7..0) = Hi-Z and B (7..0) = Hi-Z else (if G = 0) and DIR = 0
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Microprocessors Common TTL Devices used in Microprocessor Systems
3-to-8 Decoder (74XX138) Decoders Dual 2-to-4 Decoder (74XX139)
Octal Bidirectional Buffer (74XX245) Buffers Octal Buffer (74XX244) • 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) • 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)
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)
