IBM 1 Series - Page 108

Data bytes are transmitted across the adapter/device interface serially by
bit, with the least-significant bit being transmitted first. A 10- or 11-bit
start/stop frame is used for synchronization of each byte. The bit rate is
selectable on the card by jumper pins. If the device is programmed for one
stop bit, a 10-bit start/stop frame is used; if the device is programmed for
two stop bits, an 11-bit start/stop frame is used. The following bit rates
are available:
Bits per second
50
75
100
110
150
200
300
600
1200
2400
4800
9600
The teletypewriter adapter feature is code transparent, and all 256 binary
combinations can be transmitted and received. The teletypewriter adapter
feature does not transmit break characters. Received break characters
appear to the program support system as series of all 0-characters
followed by one unpredictable character. The data exchange over the
interface is not checked for parity or device-dependent control characters.
The adapter can be configured to perform initial program load (IPL).
The interrupt mask time of the program support
system used may preclude operation at these bit
rates. See “Receive Operations” in this chapter
for more details.
Data transfer between the adapter and the processor is by byte, using
direct program control (DPC) commands; however, during IPL, the
transfer is by byte, using cycle-steal.
The teletypewriter adapter feature is packaged on single circuit card that
plugs into the backpanel of the processor or the I/O expansion unit. The
backpanels on these units distribute the I/O channel signal lines to the
I/O feature card sockets. Power is obtained from the backpanel through
card connector pins except when +12 volts is required, as explained in
‘“‘Relationship to Other Features”’ in this chapter.
Teletypewriter Adapter Feature 4-3