IBM 3164 ASCII Manual page 90

To the host
To the printer
In character mode, the start bit does not always immediately follow the stop
bit of the previously sent character. During this idle time between the stop bit
and the start bit, the telecommunication line is held at mark-signal level.
In block mode, the data entered and stored in the character buffer is
transferred to the host system in continuous form when a Send (Send, Sn
Msg, or Send line) key is pressed, or the Read Buffer command is received.
The start bit immediately follows the stop bit of the transferred character.
The data stream going to the printer is almost the same as the one to the host,
however some characters are handled differently.
In normal mode, the null characters, a send mark, field attribute characters,
error symbols, and non-displayable field characters are converted to space
characters. The characters in a double height line are transferred in the same
way as those in a single height line; handled as one line. The characters in
the double width line are transferred each with a space character.
In both formatted and unformatted modes, trailing nulls and null characters
that are followed by End-of-line (EOl) are suppressed when the Print Null
option is on.
In a print operation, the CR.lF character and DEL are automatically generated
at the end of each line. The number of CR/CR.lF characters are specified by
the Line End option while the number of DEL characters are specified by the
Time Fill option of the Set Control 7 command.
The End-of-line (EOl) and time fill character sequence is as follows:
L
C
R
L
F
o
E
L
o
E
L
o
E
L
5-3