AT32UC3C1512C Automotive Atmel Corporation, AT32UC3C1512C Automotive Datasheet - Page 1232

• Manufacturer Part Number: AT32UC3C1512C Automotive
• Manufacturer: Atmel Corporation

39.6.6.2
39.6.6.3
39.6.6.4
39.6.6.5
39.6.6.6
9166C–AVR-08/11
During the direction change there can be a period when the line is not driven. The internal pullup of the
RESET_N pin keeps the signal stable when neither master or slave is actively driving the line. The RESET_N
pin
Initializing the AW
Disabling the AW
Resetting the AW
2-pin Mode
Normal reset functionality on the RESET_N pin is disabled when using aWire. However, the
user can reset the system through the RESET aWire command. During aWire operation the
RESET_N pin should not be connected to an external reset circuitry, but disconnected via a
switch or a jumper to avoid drive contention and speed problems.
Figure 39-11. Reset Circuitry and aWire.
To enable AW, the user has to send a 0x55 pattern with a baudrate of 1 kHz on the RESET_N
pin. The AW is enabled after transmitting this pattern and the user can start transmitting com-
mands. This pattern is not the sync pattern for the first command.
After enabling the awire debug interface the halt bit is set automatically to prevent the system
from running code after the interface is enabled. To make the CPU run again set halt to zero
using the HALT command.
To disable AW, the user can keep the RESET_N pin low for 100 ms. This will disable the AW,
return RESET_N to its normal function, and reset the device.
An aWire master can also disable aWire by sending the DISABLE command. After acking the
command the AW will be disabled and RESET_N returns to its normal function.
The aWire master can reset the AW slave by pulling the RESET_N pin low for 20 ms. This is
equivalent to disabling and then enabling AW.
To avoid using special hardware when using a normal UART device as aWire master, the aWire
slave has a 2-pin mode where one pin is used as input and on pin is used as output. To enable
this mode the 2_PIN_MODE command must be sent. After sending the command, all responses
will be sent on the DATAOUT pin instead of the RESET_N pin. Commands are still received on
the RESET_N pin.
Board Reset
Circuitry
Jumper
aWire master connector
RESET_N
Power Manager
AW Debug
Interface
MCU
AT32UC3C
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