HP-UX Reference (11i v2 07/12) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

b
blmode(7) blmode(7)
CBTRIG1C (DC1) is the initial trigger character sent to the terminal at the beginning of a read
request.
CBTRIG2C (DC1) is the secondary trigger character sent to the terminal after the alert character
has been received.
CBALERTC (DC2) is the alert character sent by the terminal in response to the first trigger char-
acter. It signifies that the terminal is ready to send the data block. The alert charac-
ter can be escaped by preceding it with a backslash (
\ ).
CBTERMC (RS) is sent by the terminal after the block mode transfer is complete. It signifies the
end of the data block to the computer.
The two ioctl(2) requests that apply to block mode use the
blmodeio structure, which defined in
<blmodeio.h> , and includes the following members:
unsigned long cb_flags; /* Modes */
unsigned char cb_trig1c; /* First trigger */
unsigned char cb_trig2c; /* Second trigger */
unsigned char cb_alertc; /* Alert character */
unsigned char cb_termc; /* Terminating char */
unsigned char cb_replen; /* cb_reply length */
char cb_reply[ ]; /* optional reply */
The cb_flags member controls the basic block mode protocol:
CB_BMTRANS 0000001 Enable mandatory block mode transmission.
CB_OWNTERM 0000002 Enable user control of handshake.
The
CB_BMTRANS bit is only effective when the ICANON flag in termio (7) is set. If
ICANON is clear,
all transfers are done in raw mode, regardless of the
CB_BMTRANS bit. If CB_BMTRANS is not set,
input processing is performed as described in termio(7). During this time, if the alert character is
defined and is detected anywhere in the input stream, the input buffer is flushed and block-mode
handshake is invoked. The system then sends the cb_trig2c character to the terminal, and a block
mode transfer follows. The alert character can be escaped by preceding it with a backslash (
\
).
If
CB_BMTRANS is set, then all transmissions are processed as block mode transmissions. Block
mode handshake is not required and data read is processed as block mode transfer data. Block mode
handshake can still be invoked by receipt of an alert character as the first character received. Reads
issued while the CB_BMTRANS bit is set cause any existing input buffer data to be flushed.
If CB_OWNTERM is set, reads are terminated upon receipt of a non-escaped alert character. No input
buffer flushing is performed and the alert character is returned in the data read. This allows applica-
tion code to perform its own block-mode handshaking. If the bit is clear, an alert character causes
normal block mode handshaking to be used.
The initial
cb_flags value is all-bits-cleared.
The cb_trig1c character is the initial trigger character sent to the terminal at the beginning of a read
request. The initial value is undefined (0377); i.e., no trigger character is sent.
The cb_trig2c character is the secondary trigger character sent to the terminal after the alert character
has been received. The initial value is undefined (0377).
The
cb_alertc character is the alert character sent by the terminal in response to the first trigger char-
acter sent by the computer. It signifies that the terminal is ready to transmit data. The initial value is
undefined (0377).
The cb_termc character is sent by the terminal after the block mode transfer has completed. It signifies
the end of the data block to the computer. The initial value is undefined (0377).
The cb_replen member specifies the length in bytes of the cb_reply array. The maximum length of
the cb_reply array is NBREPLY bytes. If set to zero, the cb_reply string is not used. It is initially set to
zero.
The cb_reply array contains a string to be sent out after receipt of the alert character but before the second
trigger character is sent by the computer. Any character can be included in the reply string. The number
of characters sent is specified by cb_replen . The maximum length of the cb_reply array is NBRE-
PLY
bytes. The initial value of all characters in the cb_reply array is null.
28 Hewlett-Packard Company − 2 − HP-UX 11i Version 2: December 2007 Update