Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 75
SAM9G20
12.8 SDCard Boot
The SDCard Boot program searches for a valid application in the SD Card memory.
(Boot ROM does not support high capacity SDCards.)
It looks for a boot.bin file in the root directory of a FAT12/16/32 formatted SDCard. If a valid file is found, this application is loaded into
internal SRAM and executed by branching at address 0x0000_0000 after remap. This application may be the application code or a second-
level bootloader.
Note: The bootable SDCard slot is Slot A.
12.9 EEPROM Boot
The EEPROM Boot program searches for a valid application in an EEPROM connected to the TWI address: 0x0050_0000.
If a valid application is found, this application is loaded into internal SRAM and executed by branching at address 0x0000_0000 after
remap. See “Valid Image Detection” for more information on Valid Image Detection.
12.10 SAM-BA Boot
If no valid DataFlash device has been found during the DataFlash boot sequence, the SAM-BA boot program is performed.
The SAM-BA boot principle is to:
- Wait for USB Device enumeration.
- In parallel, wait for character(s) received on the DBGU.
- Once the communication interface is identified, the application runs in an infinite loop waiting for different commands as in
Table 12-5.
• Write commands: Write a byte (O), a halfword (H) or a word (W) to the target.
- Address: Address in hexadecimal.
- Value: Byte, halfword or word to write in hexadecimal.
- Output: ‘>’.
• Read commands: Read a byte (o), a halfword (h) or a word (w) from the target.
- Address: Address in hexadecimal
- Output: The byte, halfword or word read in hexadecimal following by ‘>’
• Send a file (S): Send a file to a specified address
- Address: Address in hexadecimal
- Output: ‘>’.
Note: There is a time-out on this command which is reached when the prompt ‘>’ appears before the end of the command execution.
• Receive a file (R): Receive data into a file from a specified address
- Address: Address in hexadecimal
- NbOfBytes: Number of bytes in hexadecimal to receive
- Output: ‘>’
Table 12-5: Commands Available through the SAM-BA Boot
Command Action Argument(s) Example
O write a byte Address, Value# O200001,CA#
o read a byte Address,# o200001,#
H write a half word Address, Value# H200002,CAFE#
h read a half word Address,# h200002,#
W write a word Address, Value# W200000,CAFEDECA#
w read a word Address,# w200000,#
S send a file Address,# S200000,#
R receive a file Address, NbOfBytes# R200000,1234#
G go Address# G200200#
V display version No argument V#