Engineering Digital Design

310 CHAPTER 7 / PROGRAMMABLE LOGIC DEVICES

FIGURE 7.13

Output macrocell for V-type PAL devices showing I/O connections and cell logic. Source: PAL Device

Data Book, Advanced Micro Devices, Inc., Sunnyvale, CA, 1992.

7.5 MIXED-LOGIC INPUTS TO AND OUTPUTS FROM

ROMs, PLAs, AND PAL DEVICES

The subject of mixed-logic inputs to decoders was discussed in Subsection 6.3.2. There,

two options were given for dealing with inputs that arrive both from positive and negative

logic sources. These input rules are necessary since the decoder is normally an IC chip with

no user access to its internal structure. Because ROMs, PLAs, and PALs also exist as IC

chips, the same ...