MC68LC302 Datasheet, PDF (56/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

System Integration Block (SIB)
NOTE
If the PIT is enabled, then the PB8 pin will not generate an inter-
rupt, since the PIT uses the PB8 interrupt in the IPR, IMR, and
ISR.
The direction of each pin is determined by the corresponding bit in the PBDDR. The port pin
is configured as an input if the corresponding PBDDR bit is cleared; it is configured as an
output if the corresponding PBDDR bit is set. PBDDR11–PBDDR8 are cleared on total sys-
tem reset, configuring all PB11–PB8 pins as general-purpose input pins.When a PB11–PB8
pin is configured as an input, a high-to-low change will cause an interrupt request signal to
be sent to the IMP interrupt controller.
3.6.4 Port N
When the LC302 is in 8-bit mode (internal BUSW=0), 8 more general purpose I/O pins are
available. The signal direction for each pin is determined by the corresponding control bit in
the port N data direction register (PNDDR). The port I/O pin is configured as an input if the
corresponding PNDDR bit is cleared; it is configured as an output if the corresponding PND-
DR bit is set. The PNDAT register is used to read and write values for the Port N pins.
3.6.5 Port Registers
The I/O port consists of three memory-mapped read-write 16-bit registers for port A and
three memory-mapped read-write 16-bit registers for port B. Refer to Figure 3-2. Parallel I/
O Port Registers for the I/O port registers. The reserved bits are read as zeros.
Port A Control Register(PACNT)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
CA
-
CA CA CA CA CA CA CA CA CA CA CA
0 = I/O
1 = Peripheral
Port A Data Direction Register(PADDR)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
DA
-
DA DA DA DA DA DA DA DA DA DA DA
0 = Input
1 = Output
Port A Data Register(PADAT)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
PA
-
PA PA PA PA PA PA PA PA PA PA PA
Port B Control Register(PBCNT)
15
RESERVED
0 = I/O
1 = Peripheral
8
7
6
5
4
3
2
1
0
CB CB CB
-
CB
-
-
-
MOTOROLA
MC68LC302 REFERENCE MANUAL
3-19