AR# 17568

説明

General Description:  

The PL3 spec allows for an 8-bit data bus mode. Can Xilinx PL3 core do this? 

The PL3 core currently can only be configured with a data width of 32 bits.  

(This is true for both version 2 and 3 of the core.)

ソリューション

If you need to have an 8-bit data bus, you can ground the unused inputs and leave the outputs floating.  

According to the PL3 spec, here is what changes:  

1. The data path is an 8-bit data path instead of 32.  

2. MOD is not required at all. 

3. Parity is calculated over only 8 LSB. 

So, you could use a 32-bit core. Always zero out the 24 MSB (that is, use only data [7:0], set data [31:8] = 0). Don't hook up the mod pins on the output, and statically drive them low on the input side.  

Because this PL3 core was not specifically built for an 8-bits wide core, it requires the equivalent amount of resources as the 32-bit core.