Datasheet

701
SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
42.1.3.2 Boot ROM: Watchdog Disable
When SAM9261 boots on internal ROM (BMS =1) the watchdog timer is disabled by software. Because the
watchdog mode register is a “write once”, the system, designed to boot on an SPI DataFlash, cannot reuse the
watchdog functionality.
Problem Fix/Workaround
If the watchdog feature is mandatory for the application, the system must boot on external memory connected on
CS0 (BMS = 0).
42.1.3.3 Boot ROM: Temperature Range
The temperature range for the Boot ROM use is 0°C / 70°C.
Starting up the device outside this temperature range can lead to unpredictable behavior. If the SAM9261-based
system may have to start up at temperatures below 0°C and above 70°C, it is recommended to boot out of an
external memory connected on NCS0.
Problem Fix/Workaround
None.
42.1.3.4 Boot ROM: UDP Pad Pull-up Enable
When SAM9261 boots on internal ROM (BMS = 1), the UDP pad pull-up is enabled by software. This can lead to
an enumeration error.
Problem Fix/Workaround
Disable UDP pad pull-up at the beginning of the boot program (ex: at91bootstrap).
42.1.4 Bus Matrix
42.1.4.1 Bus Matrix: Problem with locked transfers261
Locked transfers are not correctly handled by the Bus Matrix and can lead to a system freeze up. This does not
concern ARM locked transfers.
Problem Fix/Workaround
Avoid other Bus Matrix masters locked transfers.
42.1.5 LCD
42.1.5.1 LCD: Screen shifting after a reset
When a FIFO underflow occurs, a reset of the LCD DMA and FIFO pointers is necessary.
If only LCD DMA pointers are reset (FIFO pointers not reset), the displayed image is shifted.
Problem Fix/Workaround
Apply the following sequence to correctly reset LCD DMA and FIFO pointers:
 LCD power off
 DMA disable
 Wait for DMABUSY
 DMA reset
 LCD power on
 DMA enable.
Powering LCD off, then powering LCD on, resets the FIFO pointers.
Disabling DMA, then enabling DMA, resets the DMA pointers.