WT21-A-HCI Ver la hoja de datos (PDF) - Unspecified

Número de pieza

componentes Descripción

Lista de partido

WT21-A-HCI

BLUETOOTH HCI MODULE

Unspecified 

5

Serial Peripheral Interface (SPI)

5.1

WT21 Serial Peripheral Interface (SPI)

SPI is used for debuging primarily. This section details the considerations required when

interfacing to WT21 via the SPI.

Data may be written or read one word at a time or the auto increment feature may be used to

access blocks.

5.2

Instruction Cycle

WT21 is the slave and receives commands on SPI_MOSI and outputs data on SPI_MISO. Table

8 shows the instruction cycle for an SPI transaction.

Table 8: Instruction Cycle for an SPI Transaction

With the exception of reset, SPI_CS# must be held low during the transaction. Data on

SPI_MOSI is clocked into the WT21 on the rising edge of the clock line SPI_CLK. When reading,

WT21 replies to the master on SPI_MISO with the data changing on the falling edge of the

SPI_CLK. The master provides the clock on SPI_CLK. The transaction is terminated by taking

SPI_CS# high.

Sending a command word and the address of a register for every time it is to be read or written

is a significant overhead, especially when large amounts of data are to be transferred. To

overcome this WT21 offers increased data transfer efficiency via an auto increment operation.

To invoke auto increment, SPI_CS# is kept low, which auto increments the address, while

providing an extra 16 clock cycles for each extra word to be written or read.

5.2.1 Writing to the Device

To write to WT21, the 8-bit write command (00000010) is sent first (C[7:0]) followed by a 16-

bit address (A[15:0]). The next 16-bits (D[15:0]) clocked in on SPI_MOSI are written to the

location set by the address (A). Thereafter for each subsequent 16-bits clocked in, the address

(A) is incremented and the data written to consecutive locations until the transaction terminates

when SPI_CS# is taken high.

Bluegiga Technologies Oy

Page 18 of 56

Share Link: