(a) The 7442 decoder of Figure 9-5 does not have an ENABLE input. However, we can operate it as a 3-line-to-8-line decoder by not using outputs O̅₈ and O̅₉ and by using the D input as an ENABLE. This is illustrated in Figure 9-74. Describe how this arrangement works as an enabled 1-of-8 decoder, and state how the level on D either enables or disables the outputs.

(b) Use a megafunction to create a decimal decoder with enable.

Figure 7-94

Figure 9-5

Transcribed Image Text:

ENABLE Input code Not used D C BA 7442 !!!!!!! 09 08 07 06 05 04 03 02 01 00