At91Sam7 - Segger J-Link User Manual

• AT91SAM7XC512
• AT91SAM9XE128
• AT91SAM9XE256
9.2.1

AT91SAM7

9.2.1.1 Reset strategy
The reset pin of the device is per default disabled. This means that the reset strate-
gies which rely on the reset pin (low pulse on reset) do not work per default. For this
reason a special reset strategy has been made available.
It is recommended to use this reset strategy. This special reset strategy resets the
peripherals by writing to the RSTC_CR register. Resetting the peripherals puts all
peripherals in the defined reset state. This includes memory mapping register, which
means that after reset flash is mapped to address 0. It is also possible to achieve the
same effect by writing 0x4 to the RSTC_CR register located at address 0xfffffd00.
This information is applicable to the following devices:
• AT91SAM7S (all devices)
• AT91SAM7SE (all devices)
• AT91SAM7X (all devices)
• AT91SAM7XC (all devices)
• AT91SAM7A (all devices)
9.2.1.2 Memory mapping
Either flash or RAM can be mapped to address 0. After reset flash is mapped to
address 0. In order to majlink_supported_devices.html RAM to address 0, a 1 can be
written to the RSTC_CR register. Unfortunately, this remap register is a toggle regis-
ter, which switches between RAM and flash with every time bit zero is written.
In order to achieve a defined mapping, there are two options:
1. Use the software reset described above.
2. Test if RAM is located at 0 using multiple read/write operations and testing the
results.
Clearly 1. is the easiest solution and is recommended.
This information is applicable to the following devices:
• AT91SAM7S (all devices)
• AT91SAM7SE (all devices)
• AT91SAM7X (all devices)
• AT91SAM7XC (all devices)
• AT91SAM7A (all devices)
9.2.1.3 Recommended init sequence
In order to work with an ATMEL AT91SAM7 device, it has to be initialized. The follow-
ing paragraph describes the steps of an init sequence. An example for different soft-
ware tools, such as J-Link GDB Server, IAR Workbench and RDI, is given.
• Set JTAG speed to 30kHz
• Reset target
• Perform peripheral reset
• Disable watchdog
• Initialize PLL
• Use full JTAG speed
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