HP 48g Graphing Calculator - Manual (Page 387)

The I/O Menu—Serial I/O Commands (continued)
Key Programmable
Command
Description
fc: Li f- L t BUFLEN Returns the number of characters in the
input buffer to level 2, and the error
status to level 1 (l=no framing error or
UART overrun, or 0=framing error or
UART overrun). If 0 is returned to level
1, the number of characters returned to
level 2 represents the part of the data
received before the error—you can use it
to determine where the error occurred.
Note
Although XMIT, SRECV, and BUFLEN check
the send and receive mechanisms, the integrity of
the data isn’t checked. One method to check the
integrity of data transmission is for the sending
device to append a checksum to the end of the data
being sent, and for the receiving device to verify the
checksum.
OPENIO, XMIT, SR.ECV, and SBRK automatically open the
IR/serial port using the current values of the first four lOPAR
parameters (baud, parity, receive pacing, and transmit pacing) and the
current IR/wire setting (set using in the I/O SETUP menu).
If you open the port, the input buffer can receive incoming data (up to
255 characters), even before you execute SRECV.
27
Transmitting and Printing Data 27-19