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TABLE 3-2. PARALLEL I/O PORT CONFIGURATION SUMMARY
PORT RESTRICTIONS
Port B:
None
Port C:
Performs the following
dedicated functions:
Bit 0,
I, 2:
None unless port
B i sin mode 1.
Bit 3:
INTR (Interrupt
Request) output for port
Bits 4 and 5:
Can be used for
input or output; both have same
direction.
Bit 6:
ACK* (Acknowledge)
input for port A.
Bit 7:
OBF* (Output Buffer
Full) Output for port A.
Port B:
None
Port C:
None unless port B is
in mode
1.
Port B:
None
Port C:
None unless port B is
in mode
1.
B=FFEA and C=FFEC
Port A:
None
Port C:
None unless port A is
in mode 1 or
2
Port B:
None
Port C:
Perform the following
dedicated functions:
Bit 0, I, 2:
None unl ess port
B is in mode
1.
Bit 3:
INTR (interrupt
Request) output for port A.
Bit 4:
STB* (Strobe) input for
port A.
Bit 5:
IBF (Input Buffer Full)
output for port.
Bit 6 and 7:
Can be used for
input or output.
Both have
same direction.
Port B:
None
Port C:
Performs the following
dedicated functions:
Bit 0:
Cannot be used.
Bit 1 and 2:
Can be used as
input or output if port B is in
mode O.
Bit 3:
INTR (Interrupt
Request) output for port.
Bit 4:
STR* (Strobe) input for
port A.
Bit 5:
IBF (Input Buffer Full)
output for port A.
Bit 6:
ACK* (Acknowledge)
input for port A.
Data flow
direction control for 8304 via
jumper 105-111
Bit 7:
OBF* (Output Buffer
Full) output for port A.
EFFECT
Enable
input
at U3
Enable
input
at U3
Enable
output
at 8304
Enable
input
at U3
Enable
Input
at U5
Allows
PPC6
Output
of Port
C to
Control
Di rec-
tion of
Data
Flow
104-109
As
shipped
105-111
JUMPER ACTION
LETE
ADD
me
me
105-108
As
shipp~d
me
105-108
As
shipped
)5-108
105-110
)5-108
105-110
05-108
CONTROL
CONNECTOR
DRIVER/TERMINATOR
PORT AND MODE
WORD
POLARITY
NETWORK
DE
--
I--.
A Mode 0
1001XXXX
Positive
8304 at U3
Nl
Input FFE8
True
A Mode 0
1000XXXX
Positive
8304 at U3
1l
Output
True
(Latched)
--
I---
A Mode 1
1011XXXX
Positive
8304 at U3
Nl
Inputs
True
(Strobed)
1 - - - .
A Mode 1
1010XXXX
Positive
8304 at U3
l(
Output
True
(Latched)
A Mode
2
11XXXXXX
Positive
8304 at U3
1
Bidirectional
True
- - I - - - .
B Mode 0
lXXXXOIX
Positive
8304 at U5
N<
Input FFEA
True
--'""'--.
3-9
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