Datasheet

2017 Microchip Technology Inc. DS60001516A-page 325
SAM9G20
Figure 27-2: Debug Unit Application Example
27.3 Product Dependencies
27.3.1 I/O Lines
Depending on product integration, the Debug Unit pins may be multiplexed with PIO lines. In this case, the programmer must first configure
the corresponding PIO Controller to enable I/O lines operations of the Debug Unit.
27.3.2 Power Management
Depending on product integration, the Debug Unit clock may be controllable through the Power Management Controller. In this case, the
programmer must first configure the PMC to enable the Debug Unit clock. Usually, the peripheral identifier used for this purpose is 1.
27.3.3 Interrupt Source
Depending on product integration, the Debug Unit interrupt line is connected to one of the interrupt sources of the Advanced Interrupt
Controller. Interrupt handling requires programming of the AIC before configuring the Debug Unit. Usually, the Debug Unit interrupt line
connects to the interrupt source 1 of the AIC, which may be shared with the real-time clock, the system timer interrupt lines and other
system peripheral interrupts, as shown in Figure 27-1. This sharing requires the programmer to determine the source of the interrupt when
the source 1 is triggered.
27.4 UART Operations
The Debug Unit operates as a UART, (asynchronous mode only) and supports only 8-bit character handling (with parity). It has no clock
pin.
The Debug Unit's UART is made up of a receiver and a transmitter that operate independently, and a common baud rate generator.
Receiver timeout and transmitter time guard are not implemented. However, all the implemented features are compatible with those of a
standard USART.
27.4.1 Baud Rate Generator
The baud rate generator provides the bit period clock named baud rate clock to both the receiver and the transmitter.
The baud rate clock is the master clock divided by 16 times the value (CD) written in DBGU_BRGR (Baud Rate Generator
Register). If DBGU_BRGR is set to 0, the baud rate clock is disabled and the Debug Unit's UART remains inactive. The
maximum allowable baud rate is Master Clock divided by 16. The minimum allowable baud rate is Master Clock divided by
(16 x 65536).
Table 27-1: Debug Unit Pin Description
Pin Name Description Type
DRXD Debug Receive Data Input
DTXD Debug Transmit Data Output
Debug Unit
RS232 Drivers
Programming Tool Trace Console Debug Console
Boot Program Debug Monitor Trace Manager
Baud Rate
MCK
16 CD×
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