Byrom has been a regular for Northampton throughout the 2014/15 campaign after signing on loan from Preston North End.
His Deepdale contract was cancelled by mutual consent earlier this week, paving the way for a Sixfields deal to be signed.
Manager Chris Wilder, meanwhile, thinks Saturday's game away to Exeter City will come slightly too soon for defender Zander Diamond as he steps up his return from injury.
Winger Kaid Mohamed will be out for up to three months after suffering a broken metatarsal in last weekend's draw against Southend United. He has undergone surgery to repair the break.