Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Appendix A 295
Comparing MPE/iX Systems to MPE V Systems
Software Characteristics
Another way to alleviate the problem is to lower the terminal’s
transmission speed; devices running at 4800 bps or lower will not have
this problem.
Parity Error
With an ATP on MPE V, a read that contains a parity error still
completes normally. Then, all read data is discarded. With a DTC, the
first parity error ends the read immediately and the read data is
discarded.
Parity Error in EOR
With an ATP, a parity error in the EOR character prevents the read
from completing normally. Unless a timer expires or a byte count is
satisfied, the device can hang. This is not a problem with a DTC. The
read completes when the parity error is detected and all data is
discarded.
Stripped Characters
When the terminal controller reads input from a device, certain
characters are searched for in the stream of data. When found, some of
those are stripped from the data. The differences between the MPE V
ATP and the ASC software are as follows:
•
[Esc]: This two character sequence is not stripped from the input
data on MPE/iX computers. It is stripped from input data on MPE V
computers.
•
[Esc]; This two character sequence is not stripped from input data on
MPE/iX computers. It is stripped from input data on MPE V
computers.
• LF (linefeed). Linefeeds are stripped from input data with MPE V.
With MPE/iX, linefeeds are not stripped.
System Break and Terminal States
When a system break is received, the ATP saves the EOR character, the
read timer value, and the terminal mode. Under the same
circumstances, the DTC saves all of these, plus echo. Therefore, with
ATP, if echo was disabled, it will be disabled in the Command
Interpreter (CI). With the DTC, echo is enabled and disabled when the
user resumes.
Using [Break] (and Later :RESUME) During a Read
When you are entering data or a command in a subsystem and press
[Break] (before pressing [Return]), MPE V keeps the data entered and
completes the read if the :RESUME command is entered. MPE/iX
disregards the read data.