SAM7X128_14 Datasheet, PDF (131/662 Pages) ATMEL Corporation – ARM-based Flash MCU

Figure 21-3. Xmodem Transfer Example
Host
Device
C
SOH 01 FE Data[128] CRC CRC
ACK
SOH 02 FD Data[128] CRC CRC
ACK
SOH 03 FC Data[100] CRC CRC
ACK
EOT
ACK
21.4.3 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^®, from Windows 98SE to
Windows XP^®. 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 Atmel’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.
Atmel provides an INF example to see the device as a new serial port and also provides another custom driver used by
the SAM-BA application: atm6124.sys. Refer to the document “USB Basic Application”, literature number 6123, for more
details.
21.4.3.1 Enumeration Process
The USB protocol is a master/slave protocol. This is the host that starts the enumeration sending requests to the device
through the control endpoint. The device handles standard requests as defined in the USB Specification.
Table 21-2. Handled Standard Requests
Request
Definition
GET_DESCRIPTOR
Returns the current device configuration value.
SET_ADDRESS
Sets the device address for all future device access.
SET_CONFIGURATION
Sets the device configuration.
GET_CONFIGURATION
Returns the current device configuration value.
GET_STATUS
Returns status for the specified recipient.
SET_FEATURE
Used to set or enable a specific feature.
CLEAR_FEATURE
Used to clear or disable a specific feature.
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
131