Datasheet

SAM9G20
DS60001516A-page 76  2017 Microchip Technology Inc.
•Go (G): Jump to a specified address and execute the code
- Address: Address to jump in hexadecimal
- Output: ‘>’
• Get Version (V): Return the SAM-BA boot version
- Output: ‘>’
12.10.1 DBGU Serial Port
Communication is performed through the DBGU serial port initialized to 115200 Baud, 8, n, 1.
The Send and Receive File commands use the Xmodem protocol to communicate. Any terminal performing this protocol can be used to
send the application file to the target. The size of the binary file to send depends on the SRAM size embedded in the product. In all cases,
the size of the binary file must be lower than the SRAM size because the Xmodem protocol requires some SRAM memory to work.
12.10.2 Xmodem Protocol
The Xmodem protocol supported is the 128-byte length block. This protocol uses a two-character CRC-16 to guarantee detection of a
maximum bit error.
Xmodem protocol with CRC is accurate provided both sender and receiver report successful transmission. Each block of the transfer looks
like:
<SOH><blk #><255-blk #><--128 data bytes--><checksum> in which:
-<SOH> = 01 hex
- <blk #> = binary number, starts at 01, increments by 1, and wraps 0FFH to 00H (not to 01)
- <255-blk #> = 1’s complement of the blk#.
- <checksum> = 2 bytes CRC16
Figure 12-8 shows a transmission using this protocol.
Figure 12-8: Xmodem Transfer Example
12.10.3 USB Device Port
A 48 MHz USB clock is necessary to use the USB Device port. It has been programmed earlier in the device initialization procedure with
PLLB configuration.
The device uses the USB communication device class (CDC) drivers to take advantage of the installed PC RS-232 software to talk over
the USB. The CDC class is implemented in all releases of Windows
®
, beginning with Windows 98SE. The CDC document, available at
www.usb.org, describes a way to implement devices such as ISDN modems and virtual COM ports.
The Vendor ID is Microchip’s vendor ID 0x03EB. The product ID is 0x6124. These references are used by the host operating system to
mount the correct driver. On Windows systems, the INF files contain the correspondence between vendor ID and product ID.
Host Device
SOH 01 FE Data[128] CRC CRC
C
ACK
SOH 02 FD Data[128] CRC CRC
ACK
SOH 03 FC Data[100] CRC CRC
ACK
EOT
ACK