mc9s08sg4 Freescale Semiconductor, Inc, mc9s08sg4 Datasheet - Page 76

• Manufacturer Part Number: mc9s08sg4
• Description: 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

Chapter 6 Parallel Input/Output Control
6.4
Port A[3:0] and port B[3:0] pins can be configured as external interrupt inputs and as an external means of
waking the MCU from stop3 or wait low-power modes.
The block diagram for the pin interrupts is shown
Writing to the PTxPSn bits in the port interrupt pin enable register (PTxPS) independently enables or
disables each port pin interrupt. Each port can be configured as edge sensitive or edge and level sensitive
based on the PTxMOD bit in the port interrupt status and control register (PTxSC). Edge sensitivity can
be software programmed to be either falling or rising; the level can be either low or high. The polarity of
the edge or edge and level sensitivity is selected using the PTxESn bits in the port interrupt edge select
register (PTxES).
Synchronous logic is used to detect edges. Prior to detecting an edge, enabled pin interrupt inputs must be
at the deasserted logic level. A falling edge is detected when an enabled port input signal is seen as a logic
1 (the deasserted level) during one bus cycle and then a logic 0 (the asserted level) during the next cycle.
A rising edge is detected when the input signal is seen as a logic 0 during one bus cycle and then a logic 1
during the next cycle.
6.4.1
A valid edge on an enabled pin interrupt will set PTxIF in PTxSC. If PTxIE in PTxSC is set, an interrupt
request will be presented to the CPU. Clearing of PTxIF is accomplished by writing a 1 to PTxACK in
PTxSC.
6.4.2
A valid edge or level on an enabled pin interrupt will set PTxIF in PTxSC. If PTxIE in PTxSC is set, an
interrupt request will be presented to the CPU. Clearing of PTxIF is accomplished by writing a 1 to
PTxACK in PTxSC provided all enabled pin interrupt inputs are at their deasserted levels. PTxIF will
remain set if any enabled pin interrupt is asserted while attempting to clear by writing a 1 to PTxACK.
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PIxn
PIxn
PTxES0
PTxESn
Pin Interrupts
0
0
1
1
S
S
Edge Only Sensitivity
Edge and Level Sensitivity
PTxPS0
PTxPSn
Figure 6-2. Pin Interrupt Block Diagram
MC9S08SG8 MCU Series Data Sheet, Rev. 3
PTxMOD
V
DD
D
Figure
CK
CLR
Q
6-2.
INTERRUPT FF
PORT
PTxACK
RESET
STOP
SYNCHRONIZER
STOP BYPASS
BUSCLK
PTxIE
Freescale Semiconductor
PTxIF
PTx
INTERRUPT
REQUEST