TUSB3410 datasheet(17/92 Pages) TI

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3–1

3 Detailed Controller Description

3.1

Operating Modes

The TUSB3410 controls its USB interface in response to USB commands, and this action remains the same

independent of the serial port mode selected. On the other hand, the serial port can be set up in three modes.

As with any interface device, data movement is the TUSB3410’s main function, but typically the initial configuration

and error handling consume most of the support code. The following sections describe the various modes the device

can be used in and the means of setting up the device.

3.2

USB Interface Configuration

The TUSB3410 contains onboard ROM microcode, which enables the MCU to enumerate the device as a USB

peripheral. The ROM microcode can also load application code into internal RAM from either external memory via

the I2C bus or from the host via the USB.

3.2.1

External Memory Case

After reset, the TUSB3410 is disconnected from the USB because the pullup resistor CONT bit is cleared. The

TUSB3410 checks the I2C port for the existence of valid code, if it finds valid code, it uploads the code from the

external memory device into the RAM program space. Once loaded, the TUSB3410 connects to the USB by setting

the CONT bit and enumeration and configuration are performed. This is the most likely use of the device.

3.2.2

Host Download Case

If the valid code is not found at the I2C port, the TUSB3410 connects to the USB by setting the CONT bit, and then

an enumeration and default configuration are performed. The host can then download additional microcode into RAM

to tailor the application. Then, the MCU causes a disconnect and reconnect by using the pullup resistor CONT bit

in the USBCTL register, which causes the TUSB3410 to be re-enumerated with a new configuration.

3.3

USB Data Movement

From the USB perspective, the TUSB3410 looks like a USB peripheral device. It uses endpoint 0 as its control

endpoint, as do all USB peripherals. It also configures up to three input and three output endpoints, although most

applications use one bulk input endpoint for data in, one bulk output endpoint for data out, and one interrupt endpoint

for status updates. The USB configuration likely remains the same regardless of the serial port configuration.

Most data is moved from the USB side to the UART side and vice versa using on-chip DMA transfers. Some special

cases may use programmed IO under control of the MCU.

3.4

Serial Port Setup

The serial port requires a few control registers to be written to configure its operation. This configuration likely remains

the same regardless of the data mode used. These registers include the line control register that controls the serial

word format and the divisor registers that control the baud rate.

These registers are usually controlled by the host application.

3.5

Serial Port Data Modes

The serial port can be configured in three different, although similar, data modes. Similar to the USB mode, once

configured for a specific application, it is unlikely that the mode would be changed. The different modes affect the

timing of the serial input and output or the use of the control signals. However, the basic serial-to-parallel conversion

TUSB3410 датащи(PDF) 17 Page - Texas Instruments

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