MCP2221A-ISLASHML datasheet(4/80 Pages) MICROCHIP

4 / 80 page

MCP2221A

DS20005565A-page 4

 2016 Microchip Technology Inc.

1.1

Supported Operating Systems

The following operating systems are supported:

• Windows – XP (SP3), Vista, 7, 8, 8.1 and 10

•Linux® – any distribution with support for CDC

and HID classes

•Mac OS® – all versions – beginning with 10.7

1.1.1

ENUMERATION

The MCP2221A enumerates as a composite USB

device after POR. The device enumerates as both a

Human Interface Device (HID) for I2C, GPIO control,

and as CDC for the USB-to-UART converter.

1.1.1.1

USB HID

The MCP2221A enumerates as an HID, so the device

can be configured, while the I2C and GPIO can be

controlled. A DLL package, with example applications

and tools, is supplied by Microchip on the device web

page, on the Microchip website www.microchip.com.

1.1.1.2

USB CDC

The CDC enumeration implements the USB-to-UART

data translation.

1.2

Bus Matrix Module

The Bus Matrix module is the heart of the MCP2221A.

All other modules are tied together and controlled via

the Bus Matrix module. This module manages the data

transfers between the USB and the UART, the I2C

master module, as well as the command requests

generated by the USB host controller and commands

for controlling the function of the UART, GPIO, ADC,

DAC and clock output.

1.2.1

UART

The control module interfaces to the UART and USB

modules.

1.2.2

ACCESSING THE DEVICE

The MCP2221A can be accessed for reading and

writing via USB host commands. The device cannot be

accessed or controlled via the UART interface.

1.3

UART Interface

The MCP2221A UART interface consists of the TX and

RX data signals.

The UART is configurable for several baud rates. The

available baud rates are listed in Table 1-2.

1.3.1

GET/SET LINE CODING

The GET_LINE_CODING and SET_LINE_CODING

commands are used to read and set the UART

parameters while in operation. For example, terminal

applications (e.g., Putty, RealTerm, Hyperterminal,

etc.) send the SET_LINE_COMMAND when connecting

to the port. The MCP2221A responds by setting the

baud rate only.

The other parameters (Data bits, Parity, Stop bits)

remain unchanged.

1.3.1.1

Rounding Errors

Primary baud rate settings (with associated rounding

errors) are shown in Table 1-2.

If baud rates other than the ones shown in the table are

used, the error percentage can be calculated using

Equation 1-1 to find the actual baud rate.

EQUATION 1-1:

SOLVING FOR ACTUAL

BAUD RATE

1.3.2

CUSTOM BAUD RATES

Custom baud rates are configured by sending the

SET_LINE_CODING

USB command. See Section 2.0

“USB Enumeration Process”

for more information.

Note:

MCP2221A supports only eight Data bits,

no Parity, and one Stop bit.

TABLE 1-2:

UART PRIMARY BAUD

RATES

Desired Rate

Actual rate

% Error

300

0.00%

1200

0.00%

2400

0.00%

4800

0.00%

9600

0.00%

19200

0.00%

38400

38339

0.16%

57600

57692

0.16%

115200

115385

0.16%

230400

230769

0.16%

460800

461538

0.16%

ActualRate

12MHz

int x



------------------

Where:

12MHz

DesiredBaud

-----------------------------------

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