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TABLE 3-2. PARALLEL I/O PORT CONFIGURATION SUMMARY (continued)
Port A:
Must be in mode
0
for
all four bits to be available.
Port B:
Must be in mode
0
for
all four bits to be available.
Port A:
None
Port C:
Performs the following
dedicated functions:
Bit 0:
INTR (Interrupt
Request) output for port B.
Bit 1: OBF* (Output Buffer
Full) output for port B.
Bit 2:
ACK* (Acknowledge)
input for port.
Bit 3:
Can be used as input or
output if port A is in mode
0
Bit
4
to 7:
Can be used as
input or output if port A is in
mode
0
in some combinations
where port 1 is in mode 1.
These bits are always dedicated
when port is in mode 2.
PORT RESTRICTIONS
Port A:
Must be in mode
0
for
all four bits to be available.
Port B:
Must be in mode 0 for
all four bits to be available.
Port A:
Must be in mode
0
for
all four bits to be available.
Port B:
Must be in mode
0
for
all four bits to be available.
Port A:
Must be in mode
0
for
all four bits to be available.
Port B:
Must be in mode
0
for
all four bits to be available.
Port A:
None
Port C:
Performs the following
dedicated functions:
Bit 0:
INTR (Interrupt
Request) output for port B.
Bit 1:
IBF (Input Buffer Full)
output for port E5H.
Bit 2:
STB* (Strobe) input for
port B.
Bit 3:
Can be used as input or
output if port A is in mode O.
Bits 4 to 7:
Can be used as
input or output if port A is in
mode 0 or in some combinations
where port A is in mode 1.
These bits are always dedicated
when port is in mode 2.
Port A:
None
Port C:
None unless port A is
in mode 1 or 2
104-109
104-107
Enable
Output
at U5
at
at
JUMPER ACTION
TOR
DELETE
ADD
EFFECT
104-109
104-107
Enable
Output
at U5
None
104-109
Enable
As
Input
shipped
at U5
CONTROL
CONNECTOR
DR IVER/TERMINA
PORT AND MODE
WORD
POLARITY
NETWORK
--
B Mode 0
1XXXXOOX
Positive
8304 at U5
Output
True
(Latched)
--
B Mode 1
1XXXXllX
Positive
8304 at U5
Input
True
(Strobed)
B Mode 1
1XXXXlOX
Positive
8304 at U5
Output
True
(Latched)
--"-.
C Mode 0 High
100XlOXX
Positive
Termination
Order Bits
True
Network at U4
Input FFEC
C Mode 0 Low
100XXOX1
Positive
Termination
Order Bits
True
Network at U13
Input
C Mode 0 High
100XOOXX
Posit i ve
Driver Network
Order Bits
True
U4
Output
(Latched)
C Mode 0 Low
100XXOXO
Positive
Dri ver
Networ~;
Order Bits
True
U13
Output
(Latched)
--
3-10
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