Point-To-Point Configuration; Point-To-Point Programming Information; Character Mode; Multicharacter Transfers - HP 262SA Reference Manual

Data Communications
POINT-TO-POINT CONFIGURATION
Refer to Section 3 for point-to-point configuration instructions.
POINT-TO-POINT PROGRAMMING INFORMATION
This topic discusses programming information of interest to someone who is writing a data
communications driver or controller program to communicate with this terminal in an asyn-
chronous point-to-point environment. An asynchronous point-to-point data communications
environment is characterized by a flow of characters that have been produced over random
time intervals. To achieve hardware synchronization, each character is delimited by a ((start
bit" and one or more ((stop bits".
Character Mode
When the terminal is configured for Character mode operation (BLOCK MODE disabled), the
terminal sends characters to the host computer as they are entered through the keyboard. This
mode of operation can be used for interactive or conversational exchanges between the
terminal operator and an application program.
Multicharacter Transfers
When the terminal is configured for Block mode operation (Block mode enabled), data entered
through the keyboard is queued by the terminal and sent as a block after the. key is pressed.
If handshaking is disabled, the data block is sent when the. key is pressed. When the
DCI/DC2/DCI handshake is enabled, pressing the. key causes the terminal to send a DC2 to
the host computer after a DCl is received and then send the data block when the computer
responds with another DCl. The operation of the. key is described in detail in Section 9.
There are certain other functions which always result in a multicharacter (block) data trans-
fer.
• Terminal-to-computer data transfers initiated by an
((Ec&p"
or
((Ec d"
sequence.
• User key-to-computer data transfer
C(T"
type).
• Responses to status requests from the host computer.
• Responses to cursor sensing requests from the host computer.
The driver program at the host computer must support whatever handshaking process is
configured at the terminal (no handshake, DCl trigger handshake, or DCI/DC2/DCl hand-
shake). In the latter case, the DC2 must be recognized as a request to send data and the DCI
must be sent to trigger the transfer after system buffers have been allocated to receive the data
block. Additional software support may be needed depending upon your need for terminal or
device control. The
I nhHndShk (G)
and
I nhDC2(H)
fields of the terminal configuration menu
specify which form of handshaking the terminal will use. The Terminal Configuration menu is
described in Section 3.
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