Отправлено Bill 12 января 2004 г. 17:27 В ответ на: Опять про SS пин у Atmega (SPI интерфейс) У меня такая проблема, есть один Мастер один Slave , нужно от мастера передать слэйву данные. Как мне SS пин у мастера сконфигурировать? У слэйва я понял на вход. отправлено JTAG 12 января 2004 г. 17:14

"Master Mode
When the SPI is configured as a Master (MSTR in SPCR is set), the user can determine
the direction of the SS pin.
If SS is configured as an output, the pin is a general output pin which does not affect the
SPI system. Typically, the pin will be driving the SS pin of the SPI Slave.
If SS is configured as an input, it must be held high to ensure Master SPI operation. If
the SS pin is driven low by peripheral circuitry when the SPI is configured as a Master
with the SS pin defined as an input, the SPI system interprets this as another Master
selecting the SPI as a Slave and starting to send data to it. To avoid bus contention, the
SPI system takes the following actions:
1. The MSTR bit in SPCR is cleared and the SPI system becomes a Slave. As a
result of the SPI becoming a Slave, the MOSI and SCK pins become inputs.
2. The SPIF Flag in SPSR is set, and if the SPI interrupt is enabled, and the I-bit in
SREG is set, the interrupt routine will be executed.
Thus, when interrupt-driven SPI transmission is used in Master mode, and there exists a
possibility that SS is driven low, the interrupt should always check that the MSTR bit is
still set. If the MSTR bit has been cleared by a Slave Select, it must be set by the user to
re-enable SPI Master mode."

• Ответ: — JTAG   (12.01.2004 17:53, 224 байт)
  • Для разрешения коллизий при передаче если система мультимастер. — vi   (12.01.2004 18:15, пустое)