T32UC3L0128_14 Datasheet, PDF (720/852 Pages) ATMEL Corporation – Compact Single-cycle RISC Instruction Set Including DSP Instructions

AT32UC3L0128/256
30.4 I/O Lines Description
Table 30-1.
Name
DATA
I/O Lines Description
Description
aWire data multiplexed with the RESET_N pin.
Type
Input/Output
30.5 Product Dependencies
In order to use this module, other parts of the system must be configured correctly, as described
below.
30.5.1 I/O Lines
The pin used by AW is multiplexed with the RESET_N pin. The reset functionality is the default
function of this pin. To enable the aWire functionality on the RESET_N pin the user must enable
the aWire UART user interface.
30.5.2
Power Management
If the CPU enters a sleep mode that disables clocks used by the aWire UART user interface, the
aWire UART user interface will stop functioning and resume operation after the system wakes
up from sleep mode.
30.5.3 Clocks
The aWire UART uses the internal 120 MHz RC oscillator (RC120M) as clock source for its
operation. When using the aWire UART user interface RC120M must enabled using the Clock
Request Register (see Section 30.6.1).
The clock for the aWire UART user interface (CLK_AW) is generated by the Power Manager.
This clock is enabled at reset, and can be disabled in the Power Manager. It is recommended to
disable the aWire UART user interface before disabling the clock, to avoid freezing the aWire
UART user interface in an undefined state.
30.5.4 Interrupts
The aWire UART user interface interrupt request line is connected to the interrupt controller.
Using the aWire UART user interface interrupt requires the interrupt controller to be pro-
grammed first.
30.5.5
Debug Operation
If the AW is used for debugging the aWire UART user interface will not be usable.
When an external debugger forces the CPU into debug mode, the aWire UART user interface
continues normal operation. If the aWire UART user interface is configured in a way that
requires it to be periodically serviced by the CPU through interrupts or similar, improper opera-
tion or data loss may result during debugging.
30.5.6
External Components
The AW needs an external pullup on the RESET_N pin to ensure that the pin is pulled up when
the bus is not driven.
30.6
Functional Description
The aWire UART user interface can be used as a spare Asynchronous Receiver or Transmitter
when AW is not used for debugging.
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