Rainbow Electronics RC2100 - Manual (Page 7)

RC2100
 2005 Radiocrafts AS RC2100 Data Sheet (rev. 1.0) Page 7 of 22
RC232™ Embedded Protocol
The module offers a buffered packet radio as well as an un-buffered transparent mode in the
RC232™ embedded protocol.
Using the buffered packet radio mode, all data to be sent is stored in the module before they
are transmitted by the RF circuitry. Likewise, when data is received they are stored in the
module before they are sent to the host. This allows the communication controller to add
address information and to do error check of the data. In buffered mode the UART interface is
used to communicate with the host.
If the application requires a transparent data link, the module can be configured to operate in
an un-buffered mode. In this mode the module adds only a preamble and start-of-frame bytes
to synchronize the receiver. No addressing or checksum is provided in this case. A
synchronous interface is used to transfer data to/from the host. Note however, that the
configuration of the module is done using the UART even if the un-buffered mode is used for
data transfer. See the RC232 User Manual for further information on how to configure and
use the transparent mode.
The embedded protocol, configuration commands and configuration memory is described in
general in the RC232™ User Manual. This protocol is used in a wide range of RF modules
available from Radiocrafts. Please refer to the latest revision available on Radiocrafts web-
site. Exception and additions that apply for RC2100 only is found throughout in this data
sheet.
Maximum Packet Length
In buffered mode the max number of bytes in one packet frame on the air is 127 bytes in
addition to the preamble, start-of-frame delimiter and a length byte. The 127 bytes includes
any address or CRC bytes if enabled, and a FCS (Frame Check Sequence) of two bytes
which is always appended. The maximum number of payload bytes is therefore 114 – 125
bytes depending on the configuration. The table below shows the maximum number of
payload bytes in each case.
The PACKET_LENGTH must be set accordingly to prevent buffer overflow. This is very
important when using UART hardware handshake transferring data using the maximum
packet length. The factory setting is 114 in order to prevent accidental overflow when
addressing or CRC is used.
Do note that even when CRC is turned off (CRC_MODE = 0), there is still a built in FCS at the
physical layer that will detect transmission errors. If transmission errors are detected the data
packet is rejected.
ADDRESS_MODE
(= # bytes)
CRC_MODE
(= # bytes)
FCS
(# bytes)
PACKET_LENGTH must
be set to
0 0 Always on (2) 125 or less
0 2 Always on (2) 123 or less
2 0 Always on (2) 123 or less
2 2 Always on (2) 121 or less
9 0 Always on (2) 116 or less
9 2 Always on (2) 114 or less
Addressing
The module provides two addressing schemes selected by setting ADDRESS_MODE in the
configuration memory.