mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 517

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

18.3.2.2
Read: Anytime when register is in the map
Write: Anytime when register is in the map
Port B bits 7 through 0 are associated with address lines A7 through A0 respectively and data lines D7
through 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 B (DDRB) determines the primary
direction of each pin. DDRB also determines the source of data for a read of PORTB.
This register is not in the on-chip memory map in expanded and special peripheral modes. Therefore, these
accesses will be echoed externally.
Freescale Semiconductor
Emulation Narrow with
IVIS, and Peripheral
Expanded Narrow
Expanded Wide,
Single Chip
Port B Data Register (PORTB)
To ensure that you read the value present on the PORTB pins, always wait
at least one cycle after writing to the DDRB register before reading from the
PORTB register.
Reset
W
R
AB/DB7
Bit 7
PB7
AB7
0
7
Figure 18-4. Port A Data Register (PORTB)
AB/DB6
PB6
AB6
6
0
6
MC9S12E256 Data Sheet, Rev. 1.08
AB/DB5
PB5
AB5
5
0
5
NOTE
AB/DB4
PB4
AB4
4
4
0
Chapter 18 Multiplexed External Bus Interface (MEBIV3)
AB/DB3
PB3
AB3
3
0
3
AB/DB2
PB2
AB2
2
0
2
AB/DB1
PB1
AB1
1
0
1
AB/DB0
Bit 0
PB0
AB0
0
0
517