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9-6 SA-1100
Developer’s Manual
System Control Module
9.1.1.4 GPIO Rising-Edge Detect Register (GRER) and Falling-Edge Detect
Register (GFER)
Each GPIO port can also be programmed to detect a rising-edge, falling-edge, or either transition
on a pin. When an edge is detected that matches the type of edge programmed for the pin, a status
bit is set. The interrupt controller can be programmed to signal an interrupt to the CPU or wake up
the SA-1100 from sleep mode when any one of these status bits is set.
The GPIO rising-edge and falling-edge detect registers (GRER and GFER, respectively) are used
to select the type of transition on a GPIO pin that causes a bit within the GPIO edge detect status
register (GEDR) to be set. For a given GPIO port pin, its corresponding GRER bit is set to cause a
GEDR status bit to be set when the pin transitions from logic level zero (0) to one (1). Likewise,
GFER is used to set the corresponding GEDR status bit when a transition from logic level one (1)
to zero (0) occurs. When the corresponding bits are set in both registers, either a falling- or a
rising-edge transition causes the corresponding GEDR status bit to be set.
The following table shows both the rising-edge and falling-edge enable bit locations corresponding
to all 28 port pins. For reserved bits, writes are ignored and reads return zero; a question mark
indicates that the values are unknown at reset.
GRER
Bit31302928272625242322212019181716
R/W Reserved RE27 RE26 RE25 RE24 RE23 RE22 RE21 RE20 RE19 RE18 RE17 RE16
Reset0000????????????
Bit1514131211109876543210
R/W RE15 RE14 RE13 RE12 RE11 RE10 RE9 RE8 RE7 RE6 RE5 RE4 RE3 RE2 RE1 RE0
Reset??????????????11
Bit Name Description: GPIO Rising-Edge Detect Register (GRER)
{n} RE{n}
GPIO pin n rising-edge detect (where n = 0 through 27).
0 – Disable rising-edge detect.
1 – Set corresponding GEDR status bit when a rising edge is detected on the GPIO pin.
31.. 28 — Reserved.
GFER
Reset????????????????
Bit31302928272625242322212019181716
R/W Reserved FE27 FE26 FE25 FE24 FE23 FE22 FE21 FE20 FE19 FE18 FE17 FE16
Reset0000????????????
Bit1514131211109876543210
R/W FE15 FE14 FE13 FE12 FE11 FE10 FE9 FE8 FE7 FE6 FE5 FE4 FE3 FE2 FE1 FE0
Reset??????????????11
Bit Name Description: GPIO Falling-Edge Detect Register (GRER)
{n} FE{n}
GPIO pin n falling-edge detect (where n = 0 through 27).
0 – Disable falling-edge detect.
1 – Set corresponding GEDR status bit when a falling edge is detected on the GPIO pin.
31..28 — Reserved.