wide frequency band chip selection for SERDES

Hello I have got a problem in SERDES chip selection that I would be grateful if someone helps me in this regard. First, I explain the system that we have. We want to design an STM-4 SDH system which has 5 tributary cards and 1 optical STM-4 line card.The tributary cards are of two types : E1 card and data card. The E1 tributary card which contains an SDH E1 mapper, has a 12-pin telecombus in 19.44 MHz rate in each of its transmit and receive directions (each card has 24 pins in backplane). but the Data tributary card which contains an EoS device on itself, has a 12-pin telecombus in 77.76MHz rate in each of the transmit and receive directions.The pslot of the optical line card is fixed but each of the tributary cards can sit in any position of the 5 tributary slots. to reduce the number of the pins on the backplane we want to serialize the telecombuses between the optical line card and the tributary cards. Since we do not know which of the tributary cards is inserted in in each slot we should select a SERDES which can serialize the data from both of the rates of 19.44 and 77.76 MHz (But during my searches in different vendors I haven't been able to find such a chip). I have got 2 questions.

1- As I have seen in different vendors pages, most of the SERDES devices are placed after a protocol device. for transmitting SDH telecombus data is it necessary to implement a protocol on it or not. (Why protocol specification is required?). 2- Has anyone seen any chip which supports the mentioned rates (19.44 MHz and 77.76MHz) on its parallel side or not ?

Any help in this regard is highly appreciated.

Arash

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Arash
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