mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 516

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 18 Multiplexed External Bus Interface (MEBIV3)
18.3.2.1
Read: Anytime when register is in the map
Write: Anytime when register is in the map
Port A bits 7 through 0 are associated with address lines A15 through A8 respectively and data lines
D15/D7 through D8/D0 respectively. When this port is not used for external addresses such as in
single-chip mode, these pins can be used as general-purpose I/O. Data direction register A (DDRA)
determines the primary direction of each pin. DDRA also determines the source of data for a read of
PORTA.
This register is not in the on-chip memory map in expanded and special peripheral modes. Therefore, these
accesses will be echoed externally.
516
Emulation Narrow with
IVIS, and Peripheral
Expanded Narrow AB15 and
Expanded Wide,
Single Chip
Port A Data Register (PORTA)
To ensure that you read the value present on the PORTA pins, always wait
at least one cycle after writing to the DDRA register before reading from the
PORTA register.
Reset
W
R
DB15/DB7
AB/DB15
Bit 7
PA7
0
7
Figure 18-3. Port A Data Register (PORTA)
DB14/DB6
AB14 and
AB/DB14
PA6
6
0
6
MC9S12E256 Data Sheet, Rev. 1.08
DB13/DB5
AB13 and
AB/DB13
PA5
5
0
5
NOTE
DB12/DB4
AB12 and
AB/DB12
PA4
4
4
0
DB11/DB3
AB11 and
AB/DB11
PA3
3
0
3
DB10/DB2
AB10 and
AB/DB10
PA2
2
0
2
Freescale Semiconductor
DB9/DB1
AB9 and
AB/DB9
PA1
1
0
1
DB8/DB0
AB8 and
AB/DB8
Bit 0
PA0
0
0