Serial Communications (16C452)
Bit 6
This is the Set Break Control bit. When bit 6 is a
logical 1, the serial output (SOUT) is forced to the
spacing (logical 0) state until reset by a low-level
bit 6, regardless of other transmitter activity. This
allows the CPU to alert a terminal in a computer
communications system and has no effect on the
transmitter logic. If the following sequence is used,
no erroneous or extraneous characters are transmitted
because of the break.
1.
Load an all "0s" pad character in response to
THRE.
2.
Set Break in response to the next THRE.
3.
Wait for the transmitter to be idle (TEMT = 1),
and clear break when normal transmission has
been restored.
Bit 7
Bit 7 is the Divisor Latch Access Bit (DLAB). It
must be set high (logical 1) to access the divisor
latches of the baud rate generator during any read or
write operation. DLAB must be set low (logical 0) to
access the Receiver Buffer, the Transmitter Holding
register, or the Interrupt Enable register.
8-23
Содержание ZT 8809A
Страница 15: ...Tables Table B 9 J5 Pin Assignments B 17 Table B 10 J6 Pin Assignments B 18 Table B 11 J7 Pin Assignments B 19...
Страница 334: ...Jumper Configurations W49 W48 A W47 B A B W37 W66 A W50 B C J7 W67 Figure A 11 W37 W47 50 W66 W67 Jumper Blocks A 34...
Страница 346: ...Jumper Configurations W61 W60 W62 W63 W64 A B A B W65 Figure A 13 W60 W65 Jumper Block A 46...