
GR716-DS-UM, May 2019, Version 1.29
25
www.cobham.com/gaisler
GR716
2.2.10 Debug and statistics
An external debug host can access the microcontroller Debug Support Unit (DSU) via UART
(RS232). The DSU can be used to access instruction trace buffers and registers of the LEON3FT pro-
cessor. The DSU has also support for tracing AHB accesses that can be used for performance monitor-
ing. For more information about the functionality see section 19. Since the DSU is connected to an
AMBA AHB bus and is accessed via debug communication links also connected to AMBA AHB, all
debug accesses will generate traffic over AMBA AHB. In order for the debugging to be completely
non-intrusive this debug traffic is separated from the non-debug AHB traffic.
The microcontroller includes a LEON3 statistics unit that allows the debugger to count a wide range
of events without interrupting or controlling execution. See section 41 for more information about the
LEON3 statistics unit.
The GR716 microcontroller have one dedicated Serial Debug interface. The Serial Debug unit is
directly connected to the AMBA debug bus. The Serial Debug unit have a unique AMBA address
described in chapter 2.11.
The debug interface is intended to be used during software development and have direct access to the
internal state of the processor and trace buffers. This interface can be disabled during mission via
external pin configuration i.e. tie DSU_EN to low.
The Serial Debug interface unit is fully described in section 48
2.2.11 AMBA Error detection
The microcontroller includes status registers to store information about AMBA AHB accesses trig-
gering an error response on the Main and DMA AMBA bus. Error response on the AMBA main bus is
stored in either the memory scrubber unit or AHB Status unit 2. Error response triggered on the DMA
bus is stored in the AHB Status unit 1.
The Main AMBA bus can be configured to fetch all AMBA error responses in the memory scrubber,
see chapter 7.3.3. The system default configuration is to only fetch AMBA errors from the external
memory controllers in the memory scrubber. All other AMBA error responses on the Main bus will be
fetched in the AHB Status unit 2.