MCP2150 datasheet(19/52 Pages) MICROCHIP

19 / 52 page

 2002 Microchip Technology Inc.

Preliminary

DS21655B-page 19

MCP2150

2.11

Turnaround Latency

An IR link can be compared to a one-wire data connec-

tion. The IR transceiver can transmit or receive, but not

both at the same time. A delay of one bit time is recom-

mended between the time a byte is received and

another byte is transmitted.

2.12

IR Port Baud Rate

The baud rate for the MCP2150 IR port (the TXIR and

RXIR pins) is, initially, at the default rate of 9600 baud.

The Primary device determines the maximum baud

rate that the MCP2150 will operate at. This information

is used during NDM, with the Primary device setting the

baud rate of the IR link. The maximum IR baud rate is

not required to be the same as the MCP2150’s serial

port (UART) baud rate (as determined by the

BAUD1:BAUD0 pins).

2.13

Programmable Device ID

The MCP2150 has a flexible feature that allows the

MCP2150 Device ID to be changed by the Host Con-

troller. The default ID is “Generic IrDA” and is stored in

non-volatile, electrically erasable programmable mem-

ory (EEPROM). The maximum ID String length is 19

bytes. The format of the ID EEPROM is shown in

Figure 2-11.

The ID String must only contain the ASCII characters

from 20h to 7Ah (inclusive).

The MCP2150 enters into ID String programming when

it exits the reset state and detects that the DTR pin is

high and the RTS pin is low.

A Host Controller connected to the MCP2150 would,

typically, perform the following steps to place the

MCP2150 into ID String programming mode:

Force the MCP2150 into reset (RESET pin

forced low).

Force the DTR pin high and the RTS pin low.

Release the MCP2150 from reset (RESET pin

forced high).

Wait for device to complete initialization.

TABLE 2-5:

DTR/RTS STATE & DEVICE

MODE

Once the MCP2150 is ready to receive data, the CTS

pin will be forced low. Data may now be transferred, fol-

lowing the format in Figure 2-11. The CTS pin deter-

mines the flow control and the Host Controller must

monitor this signal to ensure that the data byte may be

sent.

Once the Host Controller has sent its last byte, the DTR

pin must be set low. This ensures that, if another reset

occurs, the MCP2150 will not reenter ID String pro-

gramming mode. The MCP2150 uses the String Length

(1st byte transmitted) to determine when the ID String

programming mode has completed. This returns the

MCP2150 to normal operation.

Example 2-1 shows the firmware code for a

PIC16CXXX acting as the Host Controller to modify the

MCP2150 Device ID String.

FIGURE 2-11:

ID STRING FORMAT

DTR

RTS

After Device Reset *

Enter Normal Mode

Enter Programmable Device ID

Enter Normal Mode

* Until device initialization is complete.

Note 1: If a non-valid ID String (containing an ASCII

character not in the valid range) is

programmed, the MCP2150 will not create

a link with a Primary device.

2: The communication program supplied with

Microsoft’s Windows® operating system

(called HyperTerminal) may leave the DTR

signal high and the RTS signals low when

the program disconnects, or is closed. Care

should be taken to ensure that this does not

accidently cause the MCP2150 to enter

Device ID String Programming.

Length

ID String

1 Byte

1 to 19 Bytes

1st Byte

Transferred

Last Byte

Transferred

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