Beehive International B102 Service Manual page 95

PROGRAMMABLE LOGIC ARRAY INPUTS
MODE 0
PLA INPUT
INPUT
DESIGNATION
TERM
1 13 SEQ4
This
1 12 SEQ3
1 11
SEQ2
1 10 SEOI
1 9 SEQ5 This
DESCRIPTION
set of four inputs comes from the SEQUENCE counter and functions as
the program counter. These four inputs do not change between
Mode 0 and Mode 1.
bit indicates to the program that an ASCII ESCAPE code has been received as a
lead-in code and the next byte received is the second byte of an ESC sequence.
This bit goes active upon receipt of an actual ESC code or is set directly from
the keyboard if an E^-type operation is desired.
input indicates to the PROGRAMMABLE LOGIC ARRAY whether to interpret
the inputs as Mode 0 or Mode 1 terms.
is a function line from the keyboard which indicates to the program whether an
alphanumeric input byte should be inserted into the text or overwrite the
character under the cursor.
I 8
I 7
16-10
I 13
1 12
1 11
I 10
I 8
I 7
16-13
I 2
I 1
1 0
MODE
INSERT
MODE
This
This
BUS7- This set of seven inputs brings the bus information into the PLA. In Mode 0, the
BUS1 bus holds the contents of the data input buffer. This set is used to decode the
incoming byte, regardless of source.
SEQ4
SEQ3
SEQ2
SEQ1
FORMAT
MODE
ILLEGAL
0PN4-
0PN1
CARRY
PROTECT
BIT
XMTR
BUSY
This
MODE 1
This set of four inputs comes from the SEQJENCE counter and functions as the
^ro^ram counter. These four inputs do not change between Mode 0and
active high signal indicates to the program whether the terminal is in the
FORMAT I
m ode, where protected data is recognized.
cates to the PROGRAMMABLE
ie inputs as Mode 0 or Mode 1 terms.
This input indicates to the PROGRAMMABLE LOGICARRAY whether to interpret
the
This term is high when the cursor is taken off the displayable portion of the screen.
It also goes high for one cycle when, the stored cursor location (BCURP and
BCURL) is decremented and underflows. This indicates that the cursor has been
returned to its original location on the screen.
These four bits are outputs from the OPERATION REGISTER which indicates the
function being accomplished in Mode 1.
This input is used when the 30 millisecond timer is being used. The timer is
fired, which drops this bit low It goes high at the end of the timeout
When not being used, this bit pulses.
This input goes high when the FORMAT MODE is "on" and the byte under the
cursor is protected.
This bit is high when the transmitter is sending a byte.
C-1