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AS8510

Datasheet - Detailed Descr i p ti on

7.8 4-Wire Serial Port Interface

The SPI interface is used as interface between the AS8510 and an external micro-controller to configure the device and access the status

information. The micro-controller begins communication with the SPI which is configured as a slave. The SPI protocol is simple and the length of

each frame is an integer multiple of bytes except when a transmission is started. Each frame has 1 command bit, 7 address/configuration bits,

and one or more data bytes. The edge of CS and the level of SCLK during the start of a SPI transaction, determine the edge on which the data is

transferred from the SPI and the edge on which the data is sampled by the slave. Table 29 describes the setting of the transfer and sampling

edges of SCLK. Figure 9 shows the falling edge and rising edge for data transfer and data sampling respectively, when SCLK is HIGH on the

falling edge of CS.

Figure 9. Protocol for Serial Data Write with Length = 1

7.8.1 SPI Frame

A frame is formed by a first byte for command and address/configuration and a following bit stream that can be formed by an integer number of

bytes. Command is coded on the 1 first bit, while address is given on LSB 7 bits (see Table 30).

If the command is read or write, one or more bytes follow. When the micro-controller sends more bytes (keeping CS LOW and SCLK toggling),

the SPI interface increments the address of the previous data byte and writes/reads data to/from consecutive addresses.

Table 29. CS and SCLK

CS

SCLK

Description

FALL

LOW

Serial data transferred on rising edge of SPI clock. Sampled at falling edge of SPI clock.

FALL

HIGH

Serial data transferred on falling edge of SPI clock. Sampled at rising edge of SPI clock.

ANY

ANY

Serial data transfer edge is unchanged.

Table 30. Command Bits

Command Bits

Register Address or Transmission Configuration

C0

A6

A5

A4

A3

A2

A1

A0

Table 31. Command Bits

C0

Command

<A6:A0>

Description

0

WRITE

ADDRESS

Writes data byte on the given starting address.

1

READ

ADDRESS

Read data byte from the given starting address.

CS

SCLK

SDI

SDO

0

A6

A5

A4

A0

A1

A2

A3

D0

D1

D2

D3

D4

D5

D7

D6

Transfer edge

Sampling edge

Data D7 – D0 is moved

to Address A4..A0 here