Datasheet

TMC2590 DATASHEET (V1.0 / 2019-FEB-22) 18

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7 SPI Interface

The TMC2590 allows full control over all configuration parameters and mode bits through the SPI

interface. In SPI mode, initialization is required prior to motor operation. The SPI interface also allows

reading back status values and bits.

7.1 Bus Signals

The SPI bus on the TMC2590 has four signals:

SCK bus clock input

SDI serial data input

SDO serial data output

CSN chip select input (active low)

The slave is enabled for an SPI transaction by a low on the chip select input CSN. Bit transfer is

synchronous to the bus clock SCK, with the slave latching the data from SDI on the rising edge of SCK

and driving data to SDO following the falling edge. The most significant bit is sent first. A minimum

of 20 SCK clock cycles is required for a bus transaction with the TMC2590.

If more than 20 clocks are driven, the additional bits shifted into SDI are shifted out on SDO after a

20-clock delay through an internal shift register. This can be used for daisy chaining multiple chips.

CSN must be low during the whole bus transaction. When CSN goes high, the contents of the internal

shift register are latched into the internal control register and recognized as a command from the

master to the slave. If more than 20 bits are sent, only the last 20 bits received before the rising edge

of CSN are recognized as the command.

7.2 Bus Timing

SPI interface is synchronized to the internal system clock, which limits the SPI bus clock SCK to half

of the system clock frequency. If the system clock is based on the on-chip oscillator, an additional

10% safety margin must be used to ensure reliable data transmission. All SPI inputs as well as the

ENN input are internally filtered to avoid triggering on pulses shorter than 20ns. Figure 7.1 shows the

timing parameters of an SPI bus transaction, and the table below specifies their values.

CSN

SCK

SDI

SDO

bit19 bit18 bit0

Figure 7.1 SPI Timing

Hint

Usually this SPI timing is referred to as SPI MODE 3