The Digital Logic Level. Chapter 3. Memory. Latches To create a 1-bit memory, we need a circuit that somehow remembers previous input values. SR Latch Inputs: S (set), R(Reset) Outputs: Q and Q
S R Q(Current) Q(New)
0 0 0 0
0 0 1 1
1 0 0 1
1 0 1 1
0 1 0 0
0 1 1 0
1 1 x ?
0 0 clear to 0
1 1 set to 1
Field-programmable gate arrays (FPGAs) are chips which contain programmable logic such that we can form arbitrary logic circuit by simply loading the FPGA with appropriate configuration data.
The FPGA chip contains two primary components that are replicated many times: LUTs (LookUp Tables) and programmable interconnects.
A LUT is a small programmable memory that produces a signal output optionally to a register, which is then output to the programmable interconnect.
The programmable memory is used to create an arbitrary logic function.
Programming the LUT requires loading the memory with the appropriate responses of the combinational logic being emulated.
Figure 3-34. The logical pinout of a generic CPU. The arrows indicate input signals and output signals. The short diagonal lines indicate that multiple pins are used. For a specific CPU, a number will be given to tell how many.