SAM4L Datasheet, PDF (136/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
Figure 11-2. I/O Lines Pin Muxing Diagram
Backup
EIC pins
Backup domain
User Interface
BKUPMUX
11.5.4
11.5.5
EIC pins
GPIO Controller
M
External
U
Interrupt
X
Controller
To enable the backup pin muxing, the user should set a one to the corresponding bit of the
Backup Pin Muxing register (BKUPPMUX) in the BPM. The backup alternate function overrides
the GPIO function.
To allow the system to be waken up by an external interrupt pin in backup mode, the backup pin
muxing should be enabled.
I/O Lines Retention in Backup Mode
When the device exits the BACKUP mode by a wake up source, the I/O line configuration can be
released or stretched, based on the RET bit in the IORET register of the BPM:
• if the BPM.IORET.RET bit is set to 0: the I/O lines are released and then driven by the reset
value of the GPIO controller module.
• if the BPM.IORET.RET bit is set to 1: the Backup configuration of I/O lines are kept until the
user sets the RET bit to 0. It allows the I/O lines to be retained until the user has programmed
the GPIO controller to its correct value, preventing I/O lines from toggling during wake up.
Wakeup From BACKUP Mode
Any enabled asynchronous sources, located in the backup domain, can wake the system up.
The user should first enable the wakeup source by programming the Backup Wake up Enable
Register (BKUPWEN).
The wakeup source is stored inside the Backup Wake up Cause Register. The user can read it
once the BACKUP mode is exited and the RUN mode is back.
See ”BACKUP Mode” on page 50. in the Low Power Technique chapter to have more details.
Note: If EIC is used to wakeup the system, the Backup Pin Muxing bit must be set (See ”I/O Lines Pin
Muxing in Backup Mode” on page 135.)
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