The RSB509B is an easy to use, low cost, data
buffer IC. RS232 serial format data is received at the input pin
and stored inside the RSB509B until the host signals that it is
ready to process the data. The data can then be processed one
byte at a time, or the entire buffer contents can be sent to the
The RSB509B allows the host processor to
perform other tasks independent of the timing of incoming RS232
data. This allows single thread processors, like Parallax's
Basic STAMP, to receive up to 32 bytes of data in background.
More sophisticated processors also benefit from the use of the
RSB509B when multiple intermittent input streams need to be
The RSB509B is easily interfaced to a host via
a single bi-directional I/O pin. Configuration of the RSB509B is
also accomplished through this single I/O pin. A pulse on the
interface pin signals the RSB509B to send data contained
in its buffer. If the pulse is longer than 1200us, the RSB509B
prepares to receive one or two configuration bytes from the host. Using
this simple pulse protocol, received data bytes can be
individually retrieved and processed.
Small 8-pin DIP or SOIC package.
Only a 4MHz crystal or clock source, a
diode, and a few resistors are required for operation.
32 byte buffer receives data and
retransmits it to the host when requested.
Only one host I/O pin is required to
interface to the RSB509B.
A simple pulse protocol is used to
configure the RSB509C and to gate the output bytes.
Programmable input baud rates of 9600,
4800, 2400, or 1200 baud. Lower rates possible with slower
Input stream can be either inverted (direct
connect to RS232 levels) or true (connection to signal
receiver like MAX232 or RS1489).
Communication with host is fixed at 9600
Pulse protocol compatible with Basic
STAMP's SERIN command.
Packet modes for implementing simple
multi-drop addressed serial networks
Buffer Empty output pin for status or
Buffer Full output pin for status or