Functional Description
25.3 Functional Description
This section discusses the operational details and basic functions of the GPIO peripheral.
25.3.1 Operating Modes
Four operating modes are defined for the module:
•
Active mode: the module is running synchronously on the interface clock, interrupt can be generated
according to the configuration and the external signals.
•
Idle mode: the module is in a waiting state, interface clock can be stopped , no interrupt can be
generated. Check the chip top-level functional specification for the availability of the debouncing clock
while in Idle mode.
•
Inactive mode: the module has no activity, interface clock can be stopped, no interrupt can be
generated.
•
Disabled mode: the module is not used, internal clock paths are gated, no interrupt request can be
generated.
The Idle and Inactive modes are configured within the module and activated on request by the host
processor through system interface sideband signals. The Disabled mode is set by software through a
dedicated configuration bit. It unconditionally gates the internal clock paths not use for the system
interface. All module registers are 8, 16 or 32-bit accessible through the OCP compatible interface (little
endian encoding). In active mode, the event detection (level or transition) is performed in the GPIO
module using the interface clock. The detection’s precision is set by the frequency of this clock and the
selected internal gating scheme.
25.3.2 Clocking and Reset Strategy
25.3.2.1 Clocks
GPIO module runs using two clocks:
•
The debouncing clock is used for the debouncing sub-module logic (without the corresponding
configuration registers). This module can sample the input line and filters the input level using a
programmed delay.
•
The interface clock provided by the peripheral bus (OCP compatible system interface). It is used
through the entire GPIO module (except within the debouncing sub-module logic). It clocks the OCP
interface and the internal logic. Clock gating features allow adapting the module power consumption to
the activity.
25.3.2.2 Clocks, Gating and Active Edge Definitions
The interface clock provided by the peripheral bus (OCP compatible system interface) is used through the
entire GPIO module. Two clock domains are defined: the OCP interface and the internal logic. Each clock
domain can be controlled independently. Sampling operations for the data capture and for the events
detection are done using the rising edge. The data loaded in the data output register (GPIO_DATAOUT) is
set at the output GPIO pins synchronously with the rising edge of the interface clock.
Five clock gating features are available:
•
Clock for the system interface logic can be gated when the module is not accessed, if the AUTOIDLE
configuration bit in the system configuration register (GPIO_SYSCONFIG) is set. Otherwise, this logic
is free running on the interface clock.
•
Clock for the input data sample logic can be gated when the data in register is not accessed.
•
Four clock groups are used for the logic in the synchronous events detection. Each 8 input GPIO_V2
pins group will have a separate enable signal depending on the edge/level detection register setting. If
a group requires no detection, then the corresponding clock will be gated. All channels are also gated
using a ‘one out of N’ scheme. N can take the values 1, 2, 4 or 8. The interface clock is enabled for
this logic one cycle every N cycles. When N is equal to 1, there is no gating and this logic is free
running on the interface clock. When N is between 2 to 8, this logic is running at the equivalent
frequency of interface clock frequency divided by N.
4061
SPRUH73H – October 2011 – Revised April 2013
General-Purpose Input/Output
Copyright © 2011–2013, Texas Instruments Incorporated
