ez80f91 ZiLOG Semiconductor, ez80f91 Datasheet - Page 62

• Manufacturer Part Number: ez80f91
• Description: Ez80 Acclaimplus!? Connectivity Assp Ez80f91 Assp
• Manufacturer: ZiLOG Semiconductor

eZ80F91 ASSP
Product Specification
54
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
generates 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), you must:
1. Set Px_DR = 1
2. Set Px_ALT2 =1
3. Set Px_ALT1= 0
4. Set Px_DDR = 0
When configured for single-edge triggered interrupt mode (GPIO mode 9), the value in
the Port x Data register determines whether a positive or negative edge causes an interrupt
request. 0 in the Port x Data register bit sets the selected pin to generate an interrupt
request for falling edges. 1 in the Port x Data register bit sets the selected pin to generate
an interrupt request for rising edges. To select mode 9 from the default mode (mode 2),
you must:
1. Set Px_DR = 1
2. Set Px_ALT2 = 1
3. Set Px_ALT = 1
4. Set Px_DDR = 1
PS027001-0707
General Purpose Input/Output