S70FS01GS datasheet(13/141 Pages) CYPRESS

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S70FS01GS

Document Number: 002-03833 Rev. *C

Page 13 of 141

Signal Protocols

3.1

SPI Clock Modes

3.1.1

Single Data Rate (SDR)

The FS-S Family can be driven by an embedded microcontroller (bus master) in either of the two following clocking modes.



Mode 0

with Clock Polarity (CPOL) = 0 and, Clock Phase (CPHA) = 0



Mode 3

with CPOL = 1 and, CPHA = 1

For these two modes, input data into the device is always latched in on the rising edge of the SCK signal and the output data is

always available from the falling edge of the SCK clock signal.

The difference between the two modes is the clock polarity when the bus master is in standby mode and not transferring any data.



SCK will stay at logic low state with CPOL = 0, CPHA = 0



SCK will stay at logic high state with CPOL = 1, CPHA = 1

Figure 3.1

SPI SDR Modes Supported

Timing diagrams throughout the remainder of the document are generally shown as both mode 0 and 3 by showing SCK as both

high and low at the fall of CS#. In some cases a timing diagram may show only mode 0 with SCK low at the fall of CS#. In such a

case, mode 3 timing simply means clock is high at the fall of CS# so no SCK rising edge set up or hold time to the falling edge of

CS# is needed for mode 3.

SCK cycles are measured (counted) from one falling edge of SCK to the next falling edge of SCK. In mode 0 the beginning of the

first SCK cycle in a command is measured from the falling edge of CS# to the first falling edge of SCK because SCK is already low

at the beginning of a command.

3.1.2

Double Data Rate (DDR)

Mode 0 and Mode 3 are also supported for DDR commands. In DDR commands, the instruction bits are always latched on the rising

edge of clock, the same as in SDR commands. However, the address and input data that follow the instruction are latched on both

the rising and falling edges of SCK. The first address bit is latched on the first rising edge of SCK following the falling edge at the end

of the last instruction bit. The first bit of output data is driven on the falling edge at the end of the last access latency (dummy) cycle.

SCK cycles are measured (counted) in the same way as in SDR commands, from one falling edge of SCK to the next falling edge of

SCK. In mode 0 the beginning of the first SCK cycle in a command is measured from the falling edge of CS# to the first falling edge

of SCK because SCK is already low at the beginning of a command.

POL=0_CPHA=0_SCLK

POL=1_CPHA=1_SCLK

CS#

MSB

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