XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 88

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

Bus Control and Input/Output (I/O)
6.3 Registers
6.3.1 Port A Data Register
Data Sheet
88
Expanded wide and peripheral:
Expanded narrow:
Under certain conditions, not all registers are visible in the memory map. In special
peripheral mode, the first 16 registers associated with bus expansion are removed
from the memory map.
In expanded modes, some or all of port A, port B, and port E are used for expansion
buses and control signals. To allow emulation of the single-chip functions of these
ports, some of these registers must be rebuilt in an external port replacement unit.
In any expanded mode,
port A and port B are used for address and data lines so registers for these ports,
as well as the data direction registers for these ports, are removed from the on-chip
memory map and become external accesses.
In any expanded mode, port E pins may be needed for bus control (for example,
ECLK and R/W). To regain the single-chip functions of port E, the emulate port E
(EME) control bit in the MODE register may be set. In this special case of expanded
mode and EME set, the port E data register (PORTE) and port E data direction
register (DDRE) are removed from the on-chip memory map and become external
accesses so port E may be rebuilt externally.
Read: Anytime, if register is in the map
Write: Anytime, if register is in the map
Bits PA7–PA0 are associated with addresses ADDR15–ADDR8 and
DATA15–DATA8. When this port is not used for external addresses and data, such
as in single-chip mode, these pins can be used as general-purpose input/output
(I/O). DDRA determines the primary direction of each pin. This register is not in the
on-chip map in expanded and peripheral modes.
Address: $0000
Reset:
Read:
Write:
Figure 6-1. Port A Data Register (PORTA)
DATA15/7
ADDR15
ADDR15
DATA15
Bit 7
PA7
Bus Control and Input/Output (I/O)
DATA14/6
ADDR14
ADDR14
DATA14
PA6
6
DATA13/5
ADDR13
ADDR13
DATA13
PA5
5
DATA12/4
ADDR12
ADDR12
DATA12
Unaffected by reset
PA4
4
DATA11/3
ADDR11
ADDR11
DATA11
PA3
3
DATA10/2
ADDR10
ADDR10
DATA10
M68HC12B Family — Rev. 8.0
PA2
2
DATA9/1
ADDR9
ADDR9
DATA9
PA1
1
MOTOROLA
DATA8/0
ADDR8
ADDR8
DATA8
Bit 0
PA0