how to upsize a bus

[anon]

I am looking for a way to implement a bus width converter. input is x bits while the output is 2x. both sides run at the clock frequency. any ideas?

 

[Mark Curry]

In article <76b9fdd8-043b-4817-b5c4-cccf5a6d4720@googlegroups.com>,
anon <vadlmans@gmail.com> wrote:

I am looking for a way to implement a bus width converter. input is x
bits while the output is 2x. both sides run at the clock frequency. any ideas?

Well, to stuff zeros onto the bus (MSBs):

wire [ 2 * BUS_WIDTH - 1 : 0 ] outbus = inbus;

To replicated the LSB to the MSBs
wire [ 2 * BUS_WIDTH - 1 : 0 ] = { 2 { inbus } };

To create a stack (it depends on your handshaking):
reg [ 2 * BUS_WIDTH - 1 : 0 ] outbus;
always @( posedge clk )
outbus <= { outbus, inbus };

reg outbus_valid;
always @( posedge clk )
outbus_valid <= ~outbus_valid; // outbus is valid every other input cycle

A lot depends on you're actual spec requirements, bus protocols, etc.

Those are basic ideas. Without more details on what you're actually
looking for, it's hard to make suggestions.

Regards,

Mark

 

[anon]

On Tuesday, June 30, 2015 at 3:21:49 PM UTC-5, Mark Curry wrote:

In article <76b9fdd8-043b-4817-b5c4-cccf5a6d4720@googlegroups.com>,
anon <vadlmans@gmail.com> wrote:
I am looking for a way to implement a bus width converter. input is x
bits while the output is 2x. both sides run at the clock frequency. any ideas?

Well, to stuff zeros onto the bus (MSBs):

wire [ 2 * BUS_WIDTH - 1 : 0 ] outbus = inbus;

To replicated the LSB to the MSBs
wire [ 2 * BUS_WIDTH - 1 : 0 ] = { 2 { inbus } };

To create a stack (it depends on your handshaking):
reg [ 2 * BUS_WIDTH - 1 : 0 ] outbus;
always @( posedge clk )
outbus <= { outbus, inbus };

reg outbus_valid;
always @( posedge clk )
outbus_valid <= ~outbus_valid; // outbus is valid every other input cycle

A lot depends on you're actual spec requirements, bus protocols, etc.

Those are basic ideas. Without more details on what you're actually
looking for, it's hard to make suggestions.

Regards,

Mark

thanks Mark. Yes, i was not given much info either during a tech interview. I guess part of the test for me is to ask more probing questions, which I did not. thanks a lot for your input.