Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 268)

MFJ-1278B MULTI-MODE OPERATIONAL COMMANDS
RXBLOCK ON/OFF Mode: Packet Default: OFF
Parameters:
ON
The MFJ-1278B will send data to the terminal in RXBLOCK format.
OFF
The MFJ-1278B will send data to the terminal in standard format.
The RXBLOCK command is designed for automated operations, such as packet bulletin
board stations. It is intended to help such systems discriminate between data received from
the connected station and MFJ-1278-generated messages.
Correct operation of RXBLOCK is dependent on the AWLEN parameter getting set to 8
(bits) since the character FF hex marks the beginning of a received data unit header.
When RXBLOCK is ON, data from other stations will be sent from the MFJ-1278B in the
following format:
*$FF* L0.....L1 PID DATA
{ prefix } { length } { pid } { data }
The fields above are defined as follows:
prefix $FF
A character with all 8 bits set
length L0 The high order length of the data, length, and pid fields logically ORed
with the value $F0
L1 The low order length of the data, length, and pid fields
pid PID The Protocol IDentifier byte received for the following data field
data DATA [Optional], variable length data
For best operation it is suggested that parameters like AUTOLF, MFILTER etc. be set OFF
in order to prevent uncertainties in the size of the data field.