Theory of Operation
Preliminary
9
3.2.3
Serial Interface Mode 03 – API
Mode 03 specifies API Mode. In this mode, the OEM has control of the radio command set
detailed in Section 6.2. Packets are transmitted upon completion of the
Send_Data
command.
In API Serial Interface Mode 03, the OEM host may utilize a set of basic commands to control the
radio and system. These commands allow the customer to establish system parameters through the
programming of variables in EEPROM as well as monitoring system performance.
These commands can
only be exercised when the radio is in API Serial Interface Mode 03
. It is important to understand two
aspects of the software commands.
1.
There are only three commands that are issued
from
the client radio
to
the Client Host. These
three commands are
Out_of_range*
,
In_range*
and
Receive_data*
. The
Receive_data*
command is the only command issued from the Server radio to the Server Host. It is
important to note that these commands will
NOT
get an acknowledgement, they are signals to
the Host to alert it to incoming data, or a change of status.
2.
All remaining commands initiated by the Host
MUST
receive an acknowledge from the radio
to signal completion of the assigned task. This works as flow control for the information
going to the radio.
The server radio can receive data from a total of 75 different clients, but from only 8 different
clients in any 30 millisecond interval. It is possible that there will be multiple
Receive_data*
commands at
the same time. Since there is no reply command at the completion of
Receive_data*
, the Host must be
capable of handling up to 8
Receive_data*
commands at one time.
Note: This means that whenever a command is initiated by the radio to the Host, the Host must be
ready to accept the command and any data following the command.
Note: A full list of commands, definitions, and implementation can be found in Section 6.
3.2.4
Serial Interface Mode 04 – Transparent, Fixed Length, No Timeout
Mode 04 specifies Transparent mode with fixed length packets and no timeout. Packets will be
transmitted over the RF interface when the number of data bytes received over the interface is equal to the
buffer specified by the user in EEPROM address locations 43H and 44H.
3.2.5
Serial Interface Buffer
The serial interface buffer provides 8Kbytes of memory broken into four dynamic regions. In the
API Serial Interface Mode 03, only one region is utilized. In the Transparent Serial Interface Modes 01, 02
and 04, a buffer region is used each time a packet release condition is met. As an example, in End
Character Mode 02, if 500 bytes are transmitted followed by the specified end character, 500 bytes will be
stored in the first region and the remianing 7.5Kbytes will be dynamically allocated for the next three
packets. It is strongly recommended that CTS or upper layer protocol with acknowledgements be used by
the OEM when operating in Transparent Serial Interface Control Modes to eliminate the following system
issues:
Note: If all four buffers are filled and the OEM host continues to send data over the interface, it will
be discarded by the radio. This can be eliminated if the OEM utilizes CTS.
