The Web Site to Remember National Semiconductor's Series 32000 Family

Udo : TITAN1

I build my first NS32000 CPU board in 1985. All my systems were called TITAN with a number behind to name the generation. The first generation used a 6 MHz set of devices. In figure 1 the board is shown. From left to right the NS32081 FPU, the NS32082 MMU, the NS32016 CPU and the NS32201 TCU can be seen. The NS32202 ICU is placed on an I/O board. Later I upgraded the system to 10 MHz clock frequency. The board contains in addition to the CPU cluster one 16L8 PAL chip for address decoding, some control logic and buffers for the system bus.

Fig. 1. Top view of TITAN1 CPU board.

Fig. 2. Bottom view of TITAN1 CPU board.

Another important part of the system is the main memory. My design has 512 kbytes DRAM build with 256-kbit chips. In 1986 this was a lot of memory. The databus was wire-wrapped because I found no way through for it with only two layers of routing.

Fig. 3. Top view of TITAN1 memory board.

Fig. 4. Bottom view of TITAN1 memory board.

In the 1980's I used foils to create the masks for the photo resist coated PCB. Figure 5 shows together the foils for the top and bottom side of the TITAN1 memory board.

Fig. 5. The foils used for the TITAN1 memory board.

The system is no longer functional. The CPU board now hangs on the wall as an eye-catcher.


The second generation of my CPU boards was developed in 1999. I used the NS32532 CPU and the NS32381 FPU for it. Due to the wire-wrap technology the board runs only at 10 MHz. But I have to say that I never tried a higher speed. Look at the bottom side and you know why. The board is equipped with 16 Mbytes of EDO DRAM. Two ispLSI1016 CPLDs from Lattice are used for the control logic. The interrupt control unit NS32202 of the Series 32000 family is no longer used. Their 40 pin DIL package was too big for the new design. For the CPU and FPU I use ZIF (Zero-Insertion-Force) sockets for easy replacements.

Fig. 6. Top view of TITAN2 CPU board.

The bottom view of the board shows the confusing wires. Keep in mind that the NS32532 has separate 32 bits wide data and address busses. I will never do again such a work!

Fig. 7. Bottom view of TITAN2 CPU board.

The system is still functional but not in use any more.


The third generation of my CPU boards was developed in 2005. Again it is based on the NS32532/NS32381 duo. Finally I used modern PCB technology. I created the board with the EAGLE layout software. The board uses 4 layers. The two outer layers are used for signals and figure 7 shows a screen shot of them. Red is the top layer and blue is the bottom layer. The inner two layers distribute all the power and ground. This board is able to run the CPU and FPU at 25 MHz. An ACEX EP1K100 FPGA from Altera having around 5000 logic elements houses all the glue logic of the system. But the main advantage of this FPGA is its 5V tolerant I/O. Therefore the design needs no buffers. All the following generations of FPGAs can only be used in 3.3V systems. DRAM is 16 Mbytes again. For such a system this amount of memory seems to be absolutly sufficient. Only for the CPU I still use a ZIF socket. The smaller FPU uses a standard socket.

I had not expected to use the ZIF socket very often. But the first two CPUs I wanted to use were failing. One had a defect in the TLB of the MMU function. The other one always sets the F-flag during a CHECKB opcode. Finally the third CPU was fully functional. I still have some more CPUs. But one day the party will be over ...

Fig. 8. EAGLE layout view of TITAN3 CPU board.

For a photo of the board please look at PC532E which reuses the TITAN3 CPU board.

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