AT91SAM9G10_1 Datasheet, PDF (302/730 Pages) ATMEL Corporation – AT91 ARM Thumb-based Microcontrollers

AT91SAM9G10
The RXRDY bit triggers the PDC channel data transfer of the receiver. This results in a read of
the data in DBGU_RHR. The TXRDY bit triggers the PDC channel data transfer of the transmit-
ter. This results in a write of a data in DBGU_THR.
28.4.5
Test Modes
The Debug Unit supports three tests modes. These modes of operation are programmed by
using the field CHMODE (Channel Mode) in the mode register DBGU_MR.
The Automatic Echo mode allows bit-by-bit retransmission. When a bit is received on the DRXD
line, it is sent to the DTXD line. The transmitter operates normally, but has no effect on the
DTXD line.
The Local Loopback mode allows the transmitted characters to be received. DTXD and DRXD
pins are not used and the output of the transmitter is internally connected to the input of the
receiver. The DRXD pin level has no effect and the DTXD line is held high, as in idle state.
The Remote Loopback mode directly connects the DRXD pin to the DTXD line. The transmitter
and the receiver are disabled and have no effect. This mode allows a bit-by-bit retransmission.
Figure 28-12. Test Modes
Automatic Echo
Receiver
RXD
Transmitter
Disabled
TXD
Local Loopback
Receiver
Transmitter
Disabled _RXD
V_DD
Disabled _TXD
Remote Loopback
Receiver
VDD
Disabled
RXD
Transmitter
Disabled
TXD
28.4.6
Debug Communication Channel Support
The Debug Unit handles the signals COMMRX and COMMTX that come from the Debug Com-
munication Channel of the ARM Processor and are driven by the In-circuit Emulator.
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