WTS701MMSLASHT datasheet(20/77 Pages) WINBOND

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WTS701

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7.3.1 Command Classes

The SPI transactions to the WTS701 fall into four classes. The four classes represent variations in

how the command, and any associated data, is handled. The class of a command is defined by the

two most significant bits of the command byte. A summary of the command classes is given below

Class 0 Commands

These are commands that are executed irrespective of the state of the WTS701. That is, the

command will execute even if the device is busy or powered down. These commands are executed

internally by a hardware command interpreter. All commands not of class 0 require that the WTS701

be in a powered up state. Example of class 0 command is the Read Status (RDST) command.

Class 1 Commands

Class 1 commands require interpretation by the internal firmware of the WTS701. Class 1 commands

consist only of a command byte and command data byte. Any further data sent in a transaction is

ignored. Class 1 commands are most often used for setting a configuration register in the device or

sending commands that have no data such as the conversion pause (PAUS) command.

Class 2 Commands

Class 2 commands have associated data. After the command word, any data bytes following are

loaded into an internal FIFO buffer for processing. If this FIFO becomes full, the R/ B signal is

asserted (LOW) indicating that the host must pause data transfer. An alternative to monitoring the

R/ B line, the R/ B bit of the status register can be monitored instead (see subsection 7.3.2) or via the

RDST command. The R/ B bit cannot be used for intra-byte flow control, e.g. if a string of characters

is sent, only every other byte is checked.

Class 3 Commands

Class 3 commands have data to return to the host. The R/ B line will go to busy immediately following

the command word indicating that the WTS701 is fetching the requested data. Data is put into the

BCNT0 and BCNT1 (see subsection 7.3.4) registers and is read out in the two subsequent bytes after

R/ B is released. If more than two bytes are returned from the command, R/ B will again be asserted

until data is ready to read. The primary Class 3 commands are to read the contents of internal

configuration registers such as RREG command.

WTS701MM/T Datasheet(PDF) 20 Page - Winbond