An apparatus for implementing VCAT in both SDH and PDH signals includes an
SDH VCAT mapper coupled to a first telecom bus and a plurality of PDH
units coupled to the first telecom bus and a second telecom bus. The PDH
units read SDH VCAT bytes from the first telecom bus and write PDH VCAT
bytes to the second telecom bus according to a gapped clock. At the data
sink RS-Ack is determined before deskewing and is latched to be reported
after deskewing. During deskewing, less than the maximum delay between
members is tracked, thereby using less storage. Addressing of the
deskewing storage is computed using a remainder algorithm.