a microcomputer design problem

[denken]

I designed a microcomputer based on the book "VHDL programming by
example" by Douglas L. Perry.
The software I use is Quartus II v5.0.
The device I use is Flex10K EPF10K20RC240-4.

The memory and cpu could be synthesized separately, but after I
combined them in my top level entity as follows

m1 : mem port map (addr, vma, rw, ready,data);
u1 : cpu port map(clock, reset, ready, addr, rw, vma, data);

No logic cell was created.

Does anyone know what is wrong?

Thanks

 

[kennheinrich]

I designed a microcomputer based on the book "VHDL programming by
example" by Douglas L. Perry.
The software I use is Quartus II v5.0.
The device I use is Flex10K EPF10K20RC240-4.

The memory and cpu could be synthesized separately, but after I
combined them in my top level entity as follows

m1 : mem port map (addr, vma, rw, ready,data);
u1 : cpu port map(clock, reset, ready, addr, rw, vma, data);

No logic cell was created.

Does anyone know what is wrong?

Thanks

If you simply cross-connected your CPU bus to your memory bus, and
left only *inputs* (clk, reset) free, it is likely that the
synthesizer optimized all of the logic away. The optimizer typically
assumes that it can delete anything unobservable. If there are no
outputs to the chip pins, then *everything* is unobservable.

To prevent this from happening, try connecting your busses (addr, rw,
etc) to some IO pins on the 10K20 device and resynthesize.

- Kenn

 

[denken]

If you simply cross-connected your CPU bus to your memory bus, and
left only *inputs* (clk, reset) free, it is likely that the
synthesizer optimized all of the logic away. The optimizer typically
assumes that it can delete anything unobservable. If there are no
outputs to the chip pins, then *everything* is unobservable.

To prevent this from happening, try connecting your busses (addr, rw,
etc) to some IO pins on the 10K20 device and resynthesize.

- Kenn

Thanks, you are right, what I did was just simply connecting cpu bus
to the memory bus.
Now the problem is whenever I tried to connect any internal bus to the
chip pin, it doesn't fit into the device, the error is like this :

Error: Node "mem:m1|lpm_ram_dq:Memory|altram:sram|q[9]" has non-
registered write enable-- attempting to initialize a RAM with non-
registered write enable

The memory I used is asynchronous, because I don't want to use more
clock cycles to read and write data from the memory. Thus in the
lpm_ram_dq generic declaration, LPM_INDATA , LPM_ADDRESS_CONTROL,
LPM_OUTDATA are unregistered. Is this the reason of the error?

 

[Mike Treseler]

The memory I used is asynchronous,

Block ram is synchronous.

because I don't want to use more
clock cycles to read and write data from the memory.

You could do burst accesses.

Thus in the
lpm_ram_dq generic declaration, LPM_INDATA , LPM_ADDRESS_CONTROL,
LPM_OUTDATA are unregistered. Is this the reason of the error?

Yes.

-- Mike Treseler