Update AWS_Shell_Interface_Specification.md (#28)

Author: aws-diamant

hdk/docs/AWS_Shell_Interface_Specification.md

@@ -263,9 +263,9 @@ Each DRAM interface is accessed via an AXI-4 interface:
 
 -   AXI-4 (CL Master and DRAM controller is slave) – 512-bit AXI-4 interface to read/write DDR
 
-There is a single status signal that the DRAM interface is trained and ready for access. The addressing uses ROW/COLUMN/BANK mapping of AXI address to DRAM Row/Col/BankGroup. The Read and Write channels are serviced with roundrobin priority (equal priority).
+There is a single status signal that the DRAM interface is trained and ready for access. The addressing uses ROW/COLUMN/BANK mapping of AXI address to DRAM Row/Col/BankGroup. The Read and Write channels are serviced with roundrobin arbitration (equal priority).
 
-The DRAM interface uses  Xilinx DDR-4 Interface controller. The AXI-4 interface adheres to the Xilinx specification. User bits are added to the read data channel to signal ECC errors with the read data.
+The DRAM interface uses Xilinx DDR-4 Interface controller. The AXI-4 interface adheres to the Xilinx specification. User bits are added to the read data channel to signal ECC errors with the read data.
 
 **NOTE:** even if no DDR4 controllers are desired in the CL, the `sh_ddr.sv` block must be instantiated in the CL (parameters are used to remove DDR controllers).  If the `sh_ddr.sv` module is not instantiated the design will have build errors.