Comtech EF Data RCS11 - Manual (Page 100)

RCS11 1:1 Redundancy Switch RCS11 Remote Communications
MN-RCS11 – Revision 9 B–6
response packet is lost due to a system or internal error, the computer times out and re-transmits
the same command packet with the same to the same receiver and waits once again for
an acknowledgment or a NAK packet.
To reiterate, the format of the message block is shown in below in Table 3, Link Level Protocol
Message Block.
SYNC COUNT SRC ADDR DEST ADDR FSN OP CODE DATA BYTES CHECKSUM
Table 3. Link Level Protocol Message Block
B.2 Remote Port Packet Structure:
The RCS11 protocol is an enhancement on the DMD5000 protocol. It also uses a packet
structure format. The structure is as follows:
= Message format header character that defines the beginning of a
message. The character value is
always 0x16. (1 byte)
= Number of bytes in the field. (2 bytes)
= Identifies the address of the equipment from where the message
originated. (1 byte)
= Identifies the address of the equipment where the message is to
be sent. (1 byte)
= Frame sequence number insures correct packet
acknowledgment and data transfers. (1 byte)
= This byte identifies the message type associated with the
information data. The equipment processes the
data according to the value in this field. Return
error codes and acknowledgment are also included in
this field. (2 bytes)
<...DATA...>
= Information data. The number of data bytes in this field is
indicated by the COUNT> value.
= The modulo 256 sum of all preceding message bytes excluding
the character. (1 byte)
CAUTION
The DMD15 RLLP is not software-compatible with the following previous Radyne
products: RCU5000 and DMD4500. These products may not occupy the same
bus
while using this protocol as equipment malfunction and loss of data may occur.