AT89C5131A(2004) Просмотр технического описания (PDF) - Atmel Corporation
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AT89C5131A Datasheet PDF : 33 Pages
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Physical Layer
48 MHz Frequency Auto-
Configuration
AT89C5131A USB Bootloader
The USB norm specifies all the transfers over the USB line. The USB specification also
includes several CLASS and SUB-CLASS specifications. These stand-alone documents
are used by the manufacturer to implement a USB link between a PC and a device sup-
porting the In System Programming. Mostly, the USB specification is implemented by
hardware (automatic reply, handshakes, timings, ...) and the USB Classes and Sub-
Classes are implemented by software at a data level.
Figure 4. USB Bus Topography
Downstream Transfer: OUT
PC Driver
PC Application
PC (Host)
Upstream Transfer: IN
Device driver/API
Firmware
USB Line
Application (Device)
The USB is used to transmit information that has the following configuration:
• USB DFU using the Default Control Endpoint only (endpoint 0) with a 32 bytes
length.
• 48 MHz for USB controller: USB clock configuration performed by the bootloader
The bootloader includes a function which will automatically setup the PLL frequency
(48MHz) versus the different XTAL configuration used on the application.
The table below shows the allowed frequencies compatible with the USB bootloader
48 MHz auto-generation.
6 MHz 8 MHz 12 MHz 16 MHz 20 MHz 24 MHz 32 MHz 40 MHz 48 MHz
X1 or X2
Clock
OK
OK
OK
OK
OK
OK
OK
OK
OK
Modes
9
4287C–USB–11/04
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