MPE/iX Intrinsics Reference Manual (32650-90905)

Chapter 5 135
Command Definitions (FCONTROL - FLOCK)
FCONTROL
28/U16 Disable user block mode:
Item has no meaning; enter a value of 0 to satisfy internal requirements.
Ignored for terminals connected through PAD.
User block mode is not supported with terminal type 18.
Under system default conditions, block mode processing occurs through a
method called Hewlett-Packard block mode. The system controls the block
mode handshake if block mode transfers are being made and the program
does not need to worry about the data transfer protocol. The host
transmits a DC1 character to inform the terminal that the system is ready
to receive data. The terminal responds with a DC2 character to inform the
system that the next data transfer is a block mode transmission. The
terminal then waits for the host to send a second DC1 character to initiate
the read.
When transmitting data in block mode, the terminal must be configured to
be compatible with the system and the application requesting the block
mode transfer.
Note: Data overruns can occur during block mode transfers. The program
must check for successful completion of each read, and retry as required.
Use of timers during block mode is encouraged to eliminate port "hangs"
due to a data overrun occurring when the last character is read. The
standard block mode read timer is disabled when the user block mode
protocol is enabled.
Not reset in break mode; not reset after FCLOSE. (Default)
29/U16 Enable user block mode:
Item has no meaning; enter a value of 0 to satisfy internal requirements.
Ignored for terminals connected through PAD.
User block mode is not supported with terminal type 18.
When user block mode is enabled and block mode transfers are being
made, the program can intervene in the block mode handshake. A user
block mode transaction begins with the DC1 character and then the
program takes control of the handshake until the DC2 character is
encountered. The program can perform additional terminal control
functions, such as positioning the terminal cursor, performing status
requests, or collating additional space for buffers before continuing with
the data transfer. When the program is ready to receive block mode data,
an additional read must be issued (DC1 character) to complete the
handshake.
When transmitting data in block mode, the terminal must be configured to
be compatible with the system and the application requesting the block
mode transfer.
Note: Data overruns can occur during block mode transfers. The program
must check for successful completion of each read, and retry as required.