74LS138 is a 3-wire-8-wire decoder. There are 54ls138 and 74LS138 lines. 54ls138 is military and 74LS138 is civilian. His working principle is as follows:

① When one gate terminal (E1) is at high level and the other two gate terminals ((/ E2)) and (/ E3)) are at low level, the binary codes of address terminals (A0, A1, A2) can be translated at the corresponding output terminals of Y0 to Y7 in low level. For example, when a2a1a0 = 110, y6 outputs a low-level signal.

② E1, E2 and E3 can be cascaded into a 24 wire decoder, and a 32 wire decoder can be cascaded if an external inverter is connected.

③ If one of the gating terminals is used as the data input terminal, 74LS138 can also be used as the data distributor.

④ It can be used in 8086 decoding circuit to expand memory.

Editor’s recommendation: 74LS138 Chinese materials PDF full version free download

Detailed explanation of 74LS138 Chinese materials

54ls138 and 74LS138 are 3-wire-8-wire decoders. There are two types of 54ls138 and 74LS138. The typical values of their main electrical characteristics are as follows:

54ls138 / 74LS138 propagation delay time 22ns, power consumption 32MW, principle: when one gate (G1) is high level, the other two gate (/ (G2A) and / (G2B)) are low level, the binary code of address (a, B, c) can be translated in a corresponding output with low level.

Using G1, / (G2A) and / (G2B), it can be cascaded into 24 wire decoder; if an external inverter is connected, it can also be cascaded into 32 wire decoder. If one of the gating terminals is used as the data input terminal, 138 can also be used as the data distributor.

  Detailed explanation of 74LS138 Chinese materials

  Detailed explanation of 74LS138 Chinese materials

Figure 2 internal logic pin diagram

 

Editor’s recommendation: 74LS138 Chinese materials PDF full version free download

Pin function:

A. B, C decoding address input, G1 gate / (G2A), / (G2B) gate (low level valid); Y0 ~ Y7 decoding output (low level valid) truth table:

  Detailed explanation of 74LS138 Chinese materials

Recommended operating conditions

  Detailed explanation of 74LS138 Chinese materials

Electrical parameters

  Detailed explanation of 74LS138 Chinese materials

Dynamic characteristic table

Detailed explanation of 74LS138 Chinese materials

Tagged:

Leave a Reply

Your email address will not be published. Required fields are marked *