eZ80F91 ASSP
Product Specification
50
request for falling edges. Writing 1 to the Port x Data Register bit sets the selected pin to
generate an interrupt request for rising edges. The interrupt request remains active until 1
is written to the corresponding bit of the Port x Alternate Register 0. To select Mode 9
from the default mode (Mode 2), observe the following brief procedure.
1. Set the Port x Data Register.
2. Set Px_ALT2 = 1.
3. Set Px_ALT1 = 1.
4. Set Px_DDR = 1.
GPIO Interrupts
Each port pin is used as an interrupt source. Interrupts are either level- or edge-triggered.
Level-Triggered Interrupts
When the port is configured for level-triggered interrupts (Mode 8), the corresponding
port pin is open-drain. An interrupt request is generated when the level at the pin is the
same as the level stored in the Port x Data Register. The port pin value is sampled by the
system clock. The input pin must be held at the selected interrupt level for a minimum of
two clock periods to initiate an interrupt. The interrupt request remains active as long as
this condition is maintained at the external source.
For example, if PA3 is programmed for low-level interrupt and the pin is forced Low for
two clock cycles, an interrupt request signal is generated from that port pin and sent to the
CPU. The interrupt request signal remains active until the external device driving PA3
forces the pin high. The CPU must be enabled to respond to interrupts for the interrupt
request signal to be acted upon.
Edge-Triggered Interrupts
When the port is configured for edge-triggered interrupts, the corresponding port pin is
open-drain. If the pin receives the correct edge from an external device, the port pin gener-
ates an interrupt request signal to the CPU.
When configured for dual edge-triggered interrupt mode (GPIO Mode 6), both a rising
and a falling edge on the pin cause an interrupt request to be sent to the CPU. To select
Mode 6 from the default mode (Mode 2), observe the following brief procedure.
1. Set Px_DR = 1.
2. Set Px_ALT2 = 1.
3. Set Px_ALT1 = 0.
PS027004-0613
P R E L I M I N A R Y
General-Purpose Input/Output
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