Paradyne DMD15L operation manual Remote Port Packet Structure, Dest. Id, Fsn

DMD15/DMD15L IBS/IDR Satellite Modem User Interfaces

the same command packet with the same <FSN> to the same receiver and waits once again for an acknowledgment or a NAK packet.

To reiterate, the format of the Link Level Protocol Message Block is shown below.

SYNC	COUNT	SRC	DEST	FSN	OPCODE	DATA	CHECKSUM
		ADDR	ADDR			BYTES

4.9.2 Remote Port Packet Structure:

The Modem protocol is an enhancement on the DMD5000 protocol. It also uses a packet structure format. The structure is as follows:

<SYNC>:	Message format header character that defines the
	beginning of a message. The <SYNC> character value is
	always 0x16 (1 byte).
<BYTE COUNT>:	The number of bytes in the <DATA> field (2 bytes).
<SOURCE ID>:	Identifies the address of the equipment from where the
	message originated (1 byte).
<DEST. ID>:	Identifies the address of the equipment where the
	message is to be sent (1 byte).
<FSN>:	Frame sequence number ensures correct packet
	acknowledgment and data transfers (1 byte).
<OPCODE>:	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 <BYTE COUNT> value.
<CHECKSUM>:	The modulo 256 sum of all preceding message bytes
	excluding the <SYNC> character (1 byte).

The Modem 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.

NOTE: When transmitting a packet at 9600 baud, the Remote M&C should ensure that the timeout value between characters does not exceed the time it takes to transmit 200 characters(200 msec). If this timeout value is exceeded, the equipment will timeout.

TM051 - Rev. 5.8 4-55