UPSD3422 datasheet(113/293 Pages) STMICROELECTRONICS

113 / 293 page

uPSD34xx

IrDA interface

113/293

Table 51.

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

Table 52.

Baud rate of UART#1 for IrDA interface

22.2

Pulse width selection

The IrDA interface has two ways to modulate the standard UART1 serial stream:

An IrDA data pulse will have a constant pulse width for any bit time, regardless of the

selected baud rate.

An IrDA data pulse will have a pulse width that is proportional to the the bit time of the

selected baud rate. In this case, an IrDA data pulse width is 3/16 of its bit time, as

shown in Figure 40 on page 111.

The PULSE bit in the SFR named IRDACON determines which method above will be used.

According to the IrDA physical layer specification, for all baud rates at 115.2k bps and below,

the minimum data pulse width is 1.41µs. For a baud rate of 115.2k bps, the maximum pulse

width 2.23µs. If a constant pulse width is to be used for all baud rates (PULSE bit = 0), the

ideal general pulse width is 1.63µs, derived from the bit time of the fastest baud rate (8.68µs

bit time for 115.2k bps rate), multiplied by the proportion, 3/16.

Bit

Symbol

R/W

Definition

7:4

BR[3:0]

R,W

Specify Baud Rate (see Table 52)

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)

BR3

BR2

BR1

BR0

Baud Rate (kbps)

115.2

57.5

38.4

19.2

14.4

12.8

9.6

7.2

4.8

3.6

2.4

1.8

1.2

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