A particular type of keyboard, instead of keyboard status register (KBSR) and keyboard data register (KBDR), has only one register called keyboard status-data register (KBSDR). Bit [15] of KBSDR is ready bit and the ASCII code of the input character is placed in bits [7:0] of KBSDR. Assume the KBSDR is mapped to address xFE00 of the LC-3s memory space. Rewrite the following polling-based keyboard echo routine for this keyboard.

POLL1 LDI R0, KBSRPtr

BRzp POLL1

LDI R0, KBDRPt

POLL2 LDI R1, DSRPtr

BRzp POLL2

STI R0, DDRPtr

...

KBSRPtr .FILL xFE00

KBDRPtr .FILL xFE02

DSRPtr .FILL xFE04

DDRPtr .FILL xFE06