
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 ...