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

Appendix A 297
Comparing MPE/iX Systems to MPE V Systems
Software Characteristics
recognized as the console attention character on any device other than
the system console. (Do not attempt to move the logical console to a
terminal connected via a PAD or to a terminal with switching enabled.)
Printer Status Request
The printer status request, also known as status checking or the
HP2631B handshake, is how the controller monitors the condition of
serial printers. Under MPE V, printer status checking can be done quite
frequently. Terminal type files 21 and 22 send a status request at
FOPEN, after each record is printed, and at FCLOSE. Terminal type files
19 and 20 send an additional status request every time the printer
sends an XOFF. With MPE/iX printer type files 21 and 22, a status
request is sent only at FOPEN and FCLOSE. (Neither MPE V terminal
type 18 nor MPE/iX printer type 18 uses status checking.) Since status
checking is done less frequently with MPE/iX, serial printers have
better performance. (Printer type file 26 on MPE/iX functions the same
as terminal type 26 file on MPE V.)
Programming Considerations
The following functions have been implemented differently and apply
only to programs written to control asynchronous devices.
Changing Parity
When programmatically changing the parity checking and generation
of a specific connection (through the FCONTROL36 and FCONTROL24
intrinsics), the type of parity is determined by the value of a parameter
of the FCONTROL36 intrinsic. The differences between MPE V’s ATP
and MPE/iX’s DTC are listed in Table A-5.
Table A-5 Parity Settings with FCONTROL(36)
FCONTROL
Control Code Value
ATP DTC
0 Even parity checked on input
Eighth bit set to 0 on output
No parity checked on input
Eighth bit set to 0 on output
1 Odd parity checked on input
Eighth bit set to 1on output
No parity checked on input
Eighth bit set to 1on output
2 Even parity checked on input
Even parity generated on output
Even parity checked on input
Even parity generated on output
3 Odd parity checkedon input Odd
parity generated on output
Odd parity checked on input
Odd parity generated on output