concept
1. Standard SPI
Usually said standard SPI SPI, which is a serial peripheral interface specification, there are four signal pin: clk, cs, mosi, miso
2. Dual SPI
It is only for SPI Flash, it is not for all SPI peripherals. For SPI Flash, full-duplex is not commonly used, and therefore extends the usage mosi and miso, so that they work in half-duplex for doubling the data transfer. I.e. for Dual SPI Flash, a command byte may be transmitted into the dual mode, so mosi becomes SIO0 (serial io 0), mosi becomes SIO1 (serial io 1), so that one clock cycle becomes possible to transmit two bit data , doubling the data transfer
3. What SPI
Dual SPI and the like, but also for the SPI Flash, Qual SPI Flash adds two I / O lines (SIO2, SIO3), the purpose of the transmission is a four bit clock
So for SPI Flash, standard spi flash, dual spi, qual spi three types, corresponding to the 3-wire, 4-wire, 6-wire, at the same Clock, the more the number of lines, the higher the transmission rate.
Interface Description
1 Interface Type:
Standard SPI: CLK, /CS, DI, DO, /WP, /Hold
Dual SPI: CLK, /CS, IO0, IO1, /WP, /Hold
Quad SPI: CLK, /CS, IO0, IO1, IO2, IO3
2. Glossary
CLK (Serial Clock): a clock line
CS (Chip Select): Chip Select Interface
DI (Serial Data Input): data input port
DO (Serial Data Output): output port