mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 531

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

18.3.2.15 Port K Data Register (PORTK)
Read: Anytime
Write: Anytime
This port is associated with the internal memory expansion emulation pins. When the port is not enabled
to emulate the internal memory expansion, the port pins are used as general-purpose I/O. When port K is
operating as a general-purpose I/O port, DDRK determines the primary direction for each port K pin. A 1
causes the associated port pin to be an output and a 0 causes the associated pin to be a high-impedance
input. The value in a DDR bit also affects the source of data for reads of the corresponding PORTK
register. If the DDR bit is 0 (input) the buffered pin input is read. If the DDR bit is 1 (output) the output of
the port data register is read.
This register is not in the map in peripheral or expanded modes while the EMK control bit in MODE
register is set. Therefore, these accesses will be echoed externally.
When inputs, these pins can be selected to be high impedance or pulled up, based upon the state of the
PUPKE bit in the PUCR register.
Freescale Semiconductor
Pin Function
Port K, Bits 5:0
Port K, Bit 7
Port K, Bit 6
Alternate
Field
5:0
Reset
7
6
W
R
Port K, Bit 7 — This bit is used as an emulation chip select signal for the emulation of the internal memory
expansion, or as general-purpose I/O, depending upon the state of the EMK bit in the MODE register. While
this bit is used as a chip select, the external bit will return to its de-asserted state (V
cycle just after the negative edge of ECLK, unless the external access is stretched and ECLK is free-running
(ESTR bit in EBICTL = 0). See
this signal will be active.
Port K, Bit 6 — This bit is used as an external chip select signal for most external accesses that are not
selected by ECS (see
state the of the EMK bit in the MODE register. While this bit is used as a chip select, the external pin will return
to its de-asserted state (V
external access is stretched and ECLK is free-running (ESTR bit in EBICTL = 0).
Port K, Bits 5:0 — These six bits are used to determine which FLASH/ROM or external memory array page
is being accessed. They can be viewed as expanded addresses XAB19–XAB14 of the 20-bit address used to
access up to1M byte internal FLASH/ROM or external memory array. Alternatively, these bits can be used for
general-purpose I/O depending upon the state of the EMK bit in the MODE register.
Bit 7
ECS
0
7
XCS
6
0
6
Figure 18-20. Port K Data Register (PORTK)
Chapter 19, “Module Mapping Control
Table 18-13. PORTK Field Descriptions
DD
MC9S12E256 Data Sheet, Rev. 1.08
XAB19
) for approximately 1/4 cycle just after the negative edge of ECLK, unless the
Chapter 19, “Module Mapping Control (MMCV4)”
5
0
5
XAB18
4
0
4
Description
Chapter 18 Multiplexed External Bus Interface (MEBIV3)
XAB17
3
3
0
(MMCV4)”for more details), depending upon the
XAB16
2
2
0
for additional details on when
DD
XAB15
) for approximately 1/4
1
0
1
XAB14
Bit 0
0
0
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