
MOTOROLA
D-18
REGISTER SUMMARY
MC68331
USER’S MANUAL
D
D.3.9 PORTF0/PORTF1
— Port F Data Register
$YFFA19, $YFFA1B
PORTF is an internal data latch that can be accessed at two locations. It can be read
or written at any time. If a pin in I/O port F is configured as an output, the corresponding
bit value is driven out on the pin. When a pin is configured for output, a read of PORTF
returns the latched bit value; when a pin is configured for input, a read returns the pin
logic level.
D.3.10 DDRF
— Port F Data Direction Register
$YFFA1D
Bits in this register control the direction of the port F pin drivers when pins are config-
ured for I/O. Setting a bit configures the corresponding pin as an output; clearing a bit
configures the corresponding pin as an input. This register can be read or written at
any time.
D.3.11 PFPAR
— Port F Pin Assignment Register
$YFFA1F
Bits in this register determine the function of port F pins. Setting a bit assigns the cor-
responding pin to a control signal; clearing a bit assigns the pin to port F.
Table D-4 Port E Pin Assignments
PEPAR Bit
PEPA7
PEPA6
PEPA5
PEPA4
PEPA3
PEPA2
PEPA1
PEPA0
Port E Signal
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
Bus Control Signal
SIZ1
SIZ0
AS
DS
RMC
AVEC
DSACK1
DSACK0
15
8
7
6
5
4
3
2
1
0
NOT USED
PF7
PF6
PF5
PF4
PF3
PF2
PF1
PF0
RESET:
U
U
U
U
U
U
U
U
15
8
7
6
5
4
3
2
1
0
NOT USED
DDF7
DDF6
DDF5
DDF4
DDF3
DDF2
DDF1
DDF0
RESET:
0
0
0
0
0
0
0
0
15
8
7
6
5
4
3
2
1
0
NOT USED
PFPA7
PFPA6
PFPA5
PFPA4
PFPA3
PFPA2
PFPA1
PFPA0
RESET:
DATA9
DATA9
DATA9
DATA9
DATA9
DATA9
DATA9
DATA9