Datasheet

679
32133D–11/2011
UC3D
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 31-8. Reset Circuitry and aWire.
31.4.6.3 Initializing the AW
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.
31.4.6.4 Disabling the AW
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.
31.4.6.5 Resetting the AW
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.
31.4.6.6 2-pin Mode
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.
31.4.6.7 Baud Rate Clock
The communication speed is set by the master in the sync field of the command. The AW will
use this to resynchronize its baud rate clock and reply on this frequency. The minimum fre-
quency of the communication is 1 kHz. The maximum frequency depends on the internal clock
source for the AW (RC120M). The baud rate clock is generated by AW with the following
formula:
RESET_N
AW Debug
Interface
Jumper
MCU
Power Manager
aWire master connector
Board Reset
Circuitry