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4.4.2 BUSY
A busy indication is developed by LSI chip ME25 pin 11. This
BUSY output, normally high when the printer is not busy, goes low when
any of the following conditions occurs:
(1) CSBSY goes low - This occurs when a dummy character (TB8)
is detected at the shift register output and a prime operation
is not in progress. This indicates that the 80th character
has just been loaded into the shift register (without
a
carriage return code).
(2) PRIME goes high - This occurs during a prime operation as
described in Section 4.3.1.
(3) LFF (internal to ME25) goes high - This occurs either when a
form feed code (octal 014) is received, orif the optional TOP
OF FORM switch on the operator panel is pressed.
(Note:
If
the DSC option is used, the received FF code will first cause
the line to be printed before activating LFF). LFF is normally
reset by the trailing edge of DLYLF.
(4) LLF (internal to ME25) goes high - This occurs when a line feed
code (octal 012) is received or the optional LINE FEED switch
on the operator panel is pressed. LLF is reset by the trailing
edge of DLYLF.
(5) LTF (internal to ME25) goes high - (Similar to the LFF signal) -
LTF goes high when a vertical tab code (octal 013) is received
and is reset by the trailing edge of DLYLF.
(6) DCPRM goes low - This occurs:
(a) when a delete code (octal
177) is received, or (b) when an INPUT PRIME signal is received
at the interface connector, or (c) a power prime (PWRPRM) con-
dition exists.
(7) REMCR (internal to ME25) goes high - This occurs when a control
character is clocked into the shift register, indicating the
start of a character printing operation.
In the standard 306
printer, only the carriage return control code (octal 015) is
stored in the shift register.
4-9
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