Transmit-Type Commands - IBM 2702 Information Manual

I/o
No Op
This command is treated as a "control immediate"
and no operation is performed by the 2702/03.
Channel End and Device End are transferred in the
status byte. This command does not reset the sense
field.
Reserve
The Reserve command is valid only when the Two-
Processor Switch (TPS) feature is installed. This
command is used to achieve attachment to the channel
via the TPS feature. The Two-Processor Switch
must be in a neutral state at this time. Once attach-
ment to a channel is achieved, the Reserve command
is treated as an
I/o
No Op, with the setting of
Channel End and Device End status.
Test
I/o
The 2702/03 responds unconditionally to an all-zero
command byte during initial command selection with
the Status Modifier bit of the unit status byte. Any
existing interrupt conditions in the 2702/03 are not
cleared; the mUltiplexer channel remains unchanged.
Release
This command is valid only when the TPS feature is
installed.
If
a Release command is issued by the
attached channel to any of the valid 2702/03 addresses
for that channel, and the command is honored, then
the TPS returns to the neutral state. The 2702/03
must be command-free to honor this command.
Sadzer
On acceptance, the 2702 will set the TC field within
the addressed LCW to zero so that the terminal
control and line oscillator with the internal address
equal to zero is associated with the addressed com-
munication line. No data transfer occurs.
The 2703 treats the Sadzer command the same as
an
I/o
No Op command.
Sad one
On accepting this control order, the 2702 sets the
terminal control (TC) field within the addressed
LCW to one so that the terminal control with the
internal address equal to one is associated with the
addressed communications line. No data transfer
occurs.
The 2703 treats the Sadone command the same as
an
I/o
No Op command.
Sadtwo
On accepting this control order, the 2702 sets the
TC field within the addressed LCW to two so that
the terminal control with the internal address equal
to two is associated with the addressed communica-
tions line. No data transfer occurs.
The 2703 treats the Sadtwo command the same as
an
I/o
No Op command.
Sadthree
On accepting this control order, the 2702 sets the
TC field within the addressed LCW to three so that
the terminal control with the internal address equal
to three is associated with the addressed communi-
cations line. No data transfer occurs.
The 2703 treats the Sadthree command the same
as an
I/o
No Op command.
Set Mode (BS Conly)
This command causes one byte, designated the
adapter control word (ACW), to be transferred from
the I/O channel to the 2703. The only meaningful
bit in this byte in Bus Out position
1. If
this bit is
a "1" the IBM (Intermediate Block Mode) bit is set
in the addressed MCW-1; if this bit is a "0" the IBM
bit is reset. The Set Mode command is normally
ended by a Stop signal.
Transmit-Type Commands
Write
The Write command causes the 2702/03 to request
data characters from the
I/o
interface and to transfer
the characters to the communications channel for
transmission to a terminal.
After accepting the Write command, the 2702/03
requests characters from the I/O interface. Before
sending the first character to the data-set interface,
the 2702/03 sends a series of mark bits for one full
character time. This series of mark bits is sent to
allow the communications facilities time
to
settle
down. The receiving device mayor may not receive
all of the initial mark bits sent by the 2702/03. The
receiving device should not count on receiving bits
until it detects the start bit (space) of the first char-
acter (or two SYN character for BSC).
Operations 2- 35