UR7HCTS2-S840 Ver la hoja de datos (PDF) - Semtech Corporation

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UR7HCTS2-S840

High-Performance, Low Power Touch Screen Controller/Digitizer

Semtech Corporation 

ASYNCHRONOUS SERIAL INTERFACE (ASI) MODE

Baud rate:

The ScreenCoderTM SPI/Serial transmits data at 19200 Baud, using the recommended 4MHz oscillator.

Protocol:

In Serial mode, the ScreenCoderTM SPI/Serial supports transmission in one direction only (IC to Host). The IC starts

the transmission to the system when it has mouse/keyboard package pending. The data format is one start bit, 8

data bits, no parity and one stop bit.

1. The ScreenCoderTM SPI/Serial asserts _CTS low to indicate that a packet transfer will start.

2. The Host asserts _RTS low to indicate that it is ready to receive data.

_RTS low means that system can receive data (e.g. UART is operational).

3. The UR7HCTS2-S840 places data on TXD line when it detects the _RTS low.

4. When one package is successfully transmitted, the IC raises _CTS.

Notes on the Protocol:

To assure fast transmission, the system must assert _RTS low as soon as possible. If the system is ready to receive

the data, it doesn't have to raise _RTS between packages.

The UR7HCTS2-S840 checks _RTS after every byte transmission. If _RTS returns to high, it means that the

transmission was unsuccessful. The IC will raise _CTS to abort the transmission and the entire package will be re-

transmitted.

The maximum time of T1 is 10ms. If the system cannot assert _RTS low after 10ms of _CTS low, the IC will raise

_CTS to abort the transmission request. After that, the ScreenCoderTM SPI/Serial will try to start the transmission

again.

_CTS

_RTS

TXD

1st

Byte

Last

Byte

t1

Figure 1: Serial Transmission Timing

Copyright Semtech 2000-2001

8

DOC7-TS2-S840-DS-102

www.semtech.com

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