1 (243)

Prévia do material em texto

Step 1 of 3 6.041E The function of the decoder is shown in Table 1. CS_L A2 A0 Output to Assert 1 X X none 0 0 0 BILL_L 0 0 X 0 MART_L 0 0 1 JOAN_L 0 0 X 1 PAUL_L 0 1 0 ANNA_L 0 1 X 0 FRED_L 0 1 1 DAVE_L 0 1 X 1 KATE L Table 1 Step 2 of 3 ABEL Equations: Decoders can be customized as in Table x6.41 using ABEL, a single GAL16V8 and single 74x138 MSI decoder module decoder "Input pins "Output pins Equations BILL =CS & RD & (!A2 & !A1 & !A0); BILL =CS & RD & (!A2 & !A1 & A0); MARRY=CS & RD & (!A2 & !A1 & !A0); MARRY=CS & RD & (!A2 & A1 & !A0); JOAN=CS & RD & (!A2 & A1 & !A0); JOAN=CS & RD & (!A2 & A1 & A0); PAUL=CS & RD & (!A2 & !A1 & A0); PAUL=CS & RD & (!A2 & A1 & A0); ANNA=CS & RD & (A2 & !A1 & !A0); ANNA=CS & RD & (A2 & !A1 & A0); FRED=CS & RD & (A2 & !A1 & !A0); FRED=CS & RD & (A2 & A1 & !A0); DAVE=CS & RD & (A2 & A1 & !A0); DAVE=CS & RD & (A2 & A1 & A0); KATE =CS & RD & (A2 & !A1 & A0); KATE =CS & RD & (A2 & A1 & A0); end decoder Step 3 of 3 Customised Decoder Circuit: Depending upon the pins CS_L, RD_L and A0, A1, A2 the outputs are enabled according to Table X6.41 (or by above ABEL equations) and this inputs can be applied to Figure 1. 74x138 +5V G1 YO BILL_L CS_L G2A Y1 MARY_L RD_L- G2B_L Y2 JOAN_L Y3 PAUL_L Y4 ANNA_L A0 Y5 FRED_L A1 B Y6 DAVE_L A2 KATE_L Figure 1