Question 16.11: Draw the logic diagram of the 16R8 PAL. Explain briefly....

More sophisticated PALs replace the combinational outputs used in the 16L8 with registered outputs with feedback. An example of such a device is the 16R8 PAL shown in Fig. 16.10. Here each product term is stored into a D type f l i p-f l o p on the rising edge of a clock signal. The output from this f l i p-f l o p is used to generate an output signal but is also fed back to the input array to allow this signal to be used by other parts of the PAL. The ability of the flip-flop to remember the previous state of the device permits the implementation of a range of sequential circuits such as counters, shift registers and machines.