Buffer Flushing; Programming The Receiver And Transmitter - HP 27130A Technical Reference Manual

HP 27130A
BUFFER FLUSHING
Several control card requests are provided to flush or clear any receive or transmit records on the
card. The control card request with subfunction 1 or 2 is used to flush the current backplane
receive buffer, and to flush all the queued receive buffers, respectively. The control card request with
subfunction 3 is used to flush all the queued transmit buffers.
The current backplane receive buffer is defined to be the record for the next host read. If the
S-bit is set for the host read and if there is any data remaining, the remaining data is the current
receive buffer. If the previous read has the S-bit set and there is no remaining data, the current
backplane buffer is defined to be the next record for the host read.
If no buffer exists on the card, the control card request will be ignored.
PROGRAMMING THE RECEIVER AND TRANSMITTER
The selection of the transmission mode is programmed by using the
wee,
SF 5.
Simplex receive and simplex transmit are provided to turn off the transmitter and receiver,
respecti vely.
The character size for the receiver and the transmitter may be specified at 7 or 8 bits per charac-
ter, not including an optional bit for even or odd parity. On transmit, the user data will be
processed byte-by-byte, passing the 7 or 8 least significant bits in each byte to the transmitter,
depending on the programmed character size. A parity bit will be added by the MUX if even or odd
parity is enabled. On receive, the incoming data will be passed to the user's buffer into the 7 or 8
least significant bits of each byte,. with the unused bits being zeros. The parity bit is never
returned to the user. The character length is programmed by using
wee,
.SF 11. The format of an
asynchronous message is shown in figure 4-1.
The baud rate and the number of stop bits are programmed by using the
wee,
SF 10 and 12,
respecti vely.
4-13