UPSD3422_V01 datasheet(120/300 Pages) STMICROELECTRONICS

120 / 300 page

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IrDA interface

UPSD3422, UPSD3433, UPSD3434, UPSD3454

120/300

The UART1 serial channel can operate in one of four different modes as shown in Table 64

on page 108 in Section 21: Serial UART interfaces on page 107. However, when UART1 is

used for IrDA communication, UART1 must operate in Mode 1 only, to be compatible with

IrDA protocol up to 115.2k bps. The IrDA interface will support baud rates generated from

Timer 1 or Timer 2, just like standard UART serial communication, but with one restriction.

The transmit baud rate and receive baud rate must be the same (cannot be different rates as

is allowed by standard UART communications).

The IrDA Interface is disabled after a reset and is enabled by setting the IRDAEN Bit in the

SFR named IRDACON (Table 70 on page 120). When IrDA is disabled, the UART1's RxD

and TxD signals will bypass the internal IrDA logic and instead they are routed directly to the

pins RxD1 and TxD1 respectively. When IrDA is enabled, the IrDA pulse shaping logic is

active and resides between UART1 and the pins RxD1 and TxD1 as shown in Figure 38 on

page 119.

22.1

Baud rate selection

The IrDA standard only supports 2.4, 9.6, 19.2, and 115.2kbps. Table 73 on page 121

informs the IrDA Interface of the baud rate of UART#1 so that it can perform pulse

modulation properly. It may not be necessary to implement the BR[3:0] bits in the IRDACON

Table 70.

IRDACON register bit definition (SFR CEh, reset value 0Fh)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

–

IRDAEN

PULSE

CDIV4

CDIV3

CDIV2

CDIV1

CDIV0

Table 71.

IRDACON register bit definition

Bit

Symbol

R/W

Definition

–

Reserved

IRDAEN

IrDA Enable

0 = IrDA Interface is disabled

1 = IrDA is enabled, UART1 outputs are disconnected from

Port 1 (or Port 4)

5PULSE

IrDA Pulse Modulation Select

0 = 1.627µs

1 = 3/16 bit time pulses

4-0

CDIV[4:0]

Specify Clock Divider (see Table 74 on page 122)

Table 72.

Baud rate selection register (SFR xxh, reset value xxh)

Bit

Symbol

R/W

Definition

7:4

BR[3:0]

R,W

Specify Baud Rate (see Table 73)

3:2

PULSE

R,W

IrDA Pulse Modulation Select

0 = 3/16 bit time pulses (not recommended)

1 = 1.627µs

1:0

IRDAEN

R,W

0 = IrDA Interface is disabled

1 = IrDA is enabled, UART#1 outputs are disconnected from

Port 1 (or Port 4)

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