The 49ers added some depth at cornerback Tuesday, bringing in a veteran to replace an injured guy.
Jackson spent his first three years with the Ravens and came back two more times, and was perhaps best known for PED suspensions. He was suspended the first eight games of 2013 for his second violation, after his initial suspension in 2012.
He played four games with the Lions last season, and has also spent time with the Giants, Bengals, and Cardinals.
Franklin was an undrafted rookie from Washburn University.