STWBC2-HP datasheet(69/96 Pages) STMICROELECTRONICS

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Figure 71. Multiple byte read access with explicit address

2.2.13.3.6

Multiple byte read access with address auto-increment:

The auto-increment is activated with a specific signal of the I/F.

The first byte transmitted by the master after NSS goes low corresponds to the first access address. The MSB of

this byte is 1, meaning that it is a read access. During the transmission of the first byte, the slave transmits 8bits

data at 0.

Each following byte must be 0 to engage the auto-increment of the address. The address of the access is

automatically incremented up to 0x7F. When 0x7F is reached, the address is no more incremented.

The read process stops when NSS comes high.

Figure 72. Multiple byte read access with address auto-increment

2.2.13.3.7

Multiple byte read access at fixed address:

The auto-increment is deactivated with a specific signal of the I/F.

The first byte transmitted by the master after NSS goes low corresponds to the first access address. The MSB of

this byte is 1, meaning that it is a read access. During the transmission of the first byte, the slave transmits 8bits

data at 0.

Each following byte must be 0 to engage the fixed address access. For each byte, the slave transmits the data

read at the same address. This mode is useful to read a FIFO content at a fixed address.

The read process stops when NSS comes high.

Figure 73. Multiple byte read access at fixed address

2.2.13.3.8

Read-Modify-Write access:

The Read-Modify-Write (RMW) access allows modifying one bit or two contiguous bits at a given position in a

The first byte transmitted by the master after NSS goes low corresponds to the access address. The MSB of this

byte is 1, meaning that it is a read access. During the transmission of the first byte, the slave transmits 8bits data

at 0.

The second byte transmitted must have bit 7 = 0 and bit 6 = 1. This informs the SPI slave that access is an RMW.

Bit 5, called n, informs of the number of bits to modify. If bit 5 = 0, only 1 bit is modified. If bit 5 = 1, 2 bits are

modified.

Bit 4 & 3, called bits[1:0], gives the bit value to set in the register. If the RMW is only 1bit, the bits[0] bit is used.

Bit 2, 1 & 0, called pos[2:0], gives the position in the register byte to apply the bit modification.

STWBC2-HP

Digital AFE functions

DS13825 - Rev 1.0

page 69/96

STWBC2-HP Datasheet(PDF) 69 Page - STMicroelectronics