IBM 1 Series - Page 110

Operation at bit rates greater than 110 bps may not be achieved because
of the interrupt mask time of the program support system used.
Unbuffered devices whose inputs are from the keyboard, are generally less
affected by the interrupt mask time of the program support system. See
““Receive Operations”’ in this chapter for more details.
This interface offers signal and bit-rate selectability to accommodate a
wide range of devices.
The input options are as follows:
Type/name Data mark convention
Nonisolated contact sense Closed circuit=mark;open circuit=mark
Isolated contact sense Closed circuit=mark; open circuit=mark
TTL Minus=mark; plus=mark
EIA received data Minus (standard convention)=mark; plus=mark
These input options are selected by utilizing appropriate top-card
connector pins and by jumper pins on the card. The output signals to the
device are nonisolated solid-state switches, current drivers, and EIA
drivers.
The output options are as follows:
Type/name Data mark convention
Current driver Current out=mark; no current out=mark
Solid-state switch/TTL Closed/minus=mark; open/plus=mark
EIA transmitted data Minus (standard convention)=mark
EIA data terminal ready None (on when +12 V installed)
Usage
Solid-state switch/TTL With Write command
write control
Solid-state switch/TTL With Read command
read control
The write and read control outputs are available for device control of the
user’s hardware and are switched by modifier bit 7 of the Write and Read
commands, respectively. These outputs are not used for any standard
attachment of a teletypewriter I/O device.
Output options are selected by utilizing the appropriate top-card connector
pins.
The teletypewriter adapter operates full-duplex. Data may be transmitted
and received concurrently between the adapter and the device.
Teletypewriter Adapter Feature 4-5