MOTOROLA
36
MC68332
MC68332TS/D
AVEC — Autovector Enable
0 = External interrupt vector enabled
1 = Autovector enabled
This field selects one of two methods of acquiring the interrupt vector during the interrupt acknowledge
cycle. It is not usually used in conjunction with a chip-select pin.
If the chip select is configured to trigger on an interrupt acknowledge cycle (SPACE = 00) and the AVEC
field is set to one, the chip select automatically generates an AVEC in response to the interrupt cycle.
Otherwise, the vector must be supplied by the requesting device.
The AVEC bit must not be used in synchronous mode, as autovector response timing can vary because
of ECLK synchronization.
3.5.5 Port C Data Register
Bit values in port C determine the state of chip-select pins used for discrete output. When a pin is as-
signed as a discrete output, the value in this register appears at the output. This is a read/write register.
Bit 7 is not used. Writing to this bit has no effect, and it always returns zero when read.
3.6 General-Purpose Input/Output
SIM pins can be configured as two general-purpose I/O ports, E and F. The following paragraphs de-
scribe registers that control the ports.
A write to the port E data register is stored in the internal data latch and, if any port E pin is configured
as an output, the value stored for that bit is driven on the pin. A read of the port E data register returns
the value at the pin only if the pin is configured as a discrete input. Otherwise, the value read is the value
stored in the register.
The port E data register is a single register that can be accessed in two locations. When accessed at
$YFFA11, the register is referred to as PORTE0; when accessed at $YFFA13, the register is referred
to as PORTE1. The register can be read or written at any time. It is unaffected by reset.
The bits in this register control the direction of the pin drivers when the pins are configured as I/O. Any
bit in this register set to one configures the corresponding pin as an output. Any bit in this register
cleared to zero configures the corresponding pin as an input. This register can be read or written at any
time.
PORTC
— Port C Data Register
$YFFA41
15
8
7
6
5
4
3
2
1
0
NOT USED
0
PC6
PC5
PC4
PC3
PC2
PC1
PC0
RESET:
0
1
1
1
1
1
1
1
PORTE0, PORTE1
—Port E Data Register
$YFFA11, $YFFA13
15
8
7
6
5
4
3
2
1
0
NOT USED
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
RESET:
U
U
U
U
U
U
U
U
DDRE
— Port E Data Direction Register
$YFFA15
15
8
7
6
5
4
3
2
1
0
NOT USED
DDE7
DDE6
DDE5
DDE4
DDE3
DDE2
DDE1
DDE0
RESET:
0
0
0
0
0
0
0
0