SAM7S256_14 Datasheet, PDF (221/775 Pages) ATMEL Corporation – ARM-based Flash MCU

Figure 26-10. Transmitter Control
DBGU_THR
Data 0
Shift Register
Data 0
DTXD
S
Data 0
P
stop
S
TXRDY
TXEMPTY
Data 1
Data 1
Data 1
P
stop
Write Data 0 Write Data 1
in DBGU_THR in DBGU_THR
26.4.4 Peripheral Data Controller
Both the receiver and the transmitter of the Debug Unit's UART are generally connected to a Peripheral Data Con-
troller (PDC) channel.
The peripheral data controller channels are programmed via registers that are mapped within the Debug Unit user
interface from the offset 0x100. The status bits are reported in the Debug Unit status register DBGU_SR and can
generate an interrupt.
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 transmitter. This results in a write of a
data in DBGU_THR.
26.4.5 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.
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
221