10-24
Intel® PXA255 Processor
Developer’s Manual
UARTs
10.4.6.2
Operation
The SIR modulation technique works with 5-, 6-, 7-, or 8-bit characters with an optional parity bit.
The data is preceded by a zero value start bit and ends with one or more stop bits. The encoding
scheme is to set a pulse 3/16 of a bit wide in the middle of every zero bit and send no pulses for bits
that are ones. The pulse for each zero bit must occur, even for consecutive bits with no edge
between them.
Table 10-17. ISR Bit Definitions
Base+0x20
Infrared Selection Register
UART
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
reserved
RXP
L
TXPL
XM
O
D
E
RCV
EI
R
X
M
ITIR
Reset 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bits
Name
Description
31:5
—
reserved
4
RXPL
Receive Data Polarity:
0 – SIR decoder interprets positive pulses as zeroes
1 – SIR decoder interprets negative pulses as zeroes
3
TXPL
Transmit Data Polarity:
0 – SIR encoder generates a positive pulse for a data bit of zero
1 – SIR encoder generates a negative pulse for a data bit of zero
2
XMODE
Transmit Pulse Width Select: When XMODE is cleared, the UART 16X clock is used to
clock the IRDA transmit and receive logic. When XMODE is set, the transmit encoder
generates 1.6
µ
s pulses (that are 3/16 of a bit time at 115.2 kbps) instead of pulses 3/16 of
a bit time wide, and the receive decoder expects pulses will be 1.6
µ
s wide also.
0 – Transmit pulse width is 3/16 of a bit time wide
1 – Transmit pulse width is 1.6
µ
s
1
RCVEIR
Receiver SIR Enable: When RCVEIR is set, the signal from the RXD pin is processed by
the IRDA decoder before it is fed to the UART. If RCVEIR is cleared, then all clocking to the
IRDA decoder is blocked and the RXD pin is fed directly to the UART.
0 – Receiver is in UART mode
1 – Receiver is in infrared mode
0
XMITIR
Transmitter SIR Enable: When XMITIR is set to a 1, the normal TXD output from the UART
is processed by the IRDA encoder before it is fed to the device pin. If XMITIR is cleared, all
clocking to the IRDA encoder is blocked and the UART’s TXD signal is connected directly
to the device pin.
When Transmitter SIR Enable is set, the TXD output pin, which is in a normally high default
state, will switch to a normally low default state. This can cause a false start bit unless the
infrared LED is disabled before XMITIR is set.
0 – Transmitter is in UART mode
1 – Transmitter is in infrared mode
Содержание PXA255
Страница 1: ...Intel PXA255 Processor Developer s Manual January 2004 Order Number 278693 002 ...
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Страница 30: ...1 6 Intel PXA255 Processor Developer s Manual Introduction ...
Страница 310: ...7 46 Intel PXA255 Processor Developer s Manual LCD Controller ...
Страница 330: ...8 20 Intel PXA255 Processor Developer s Manual Synchronous Serial Port Controller ...
Страница 358: ...9 28 Intel PXA255 Processor Developer s Manual I2 C Bus Interface Unit ...
Страница 488: ...13 36 Intel PXA255 Processor Developer s Manual AC 97 Controller Unit ...
Страница 572: ...16 30 Intel PXA255 Processor Developer s Manual Network SSP Serial Port ...
Страница 599: ...Intel PXA255 Processor Developer s Manual 17 27 Hardware UART ...
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