Cirrus Logic CS5464 - Manual (Page 23)

CS5464
DS682F3 23
7.4 Command Interface
Commands and data are transferred most-significant bit
(MSB) first.
Figure 1 on page 12, defines the serial port
timing. Commands are clocked in on SDI using SCLK.
They are a single byte (8 bits) long and fall into one of
four basic types:
1. Register Read
2. Register Write
3. Synchronizing
4. Instructions
Register reads will cause up to four bytes of register
data to be clocked out, MSB first on the SDO pin by
SCLK. During this time, other commands can be
clocked in on the SDI pin. Other commands will not in-
terrupt read data, except another register read, which
will cause the new read data to appear on SDO.
Synchronizing can be sent while read data is being
clocked out if no other commands need to be sent.
Synchronizing commands are also used to synchronize
the serial port to a byte boundary. The CS and RESET
pins will also synchronize the serial port.
Register writes require three bytes of write data to fol-
low, clocked in on the SDI pin, MSB first by SCLK.
Instructions are commands that will interrupt any in-
struction currently executing and begin the new instruc-
tion. These include conversions, calibrations, power
control, and soft reset.
(See Section 7.6 Commands on page 24).
7.5 Register Paging
Read and Write commands access one of 32 registers
within a specified page. The Resgister Page Select reg-
ister’s (Page) default value is 0. To access registers in
another page, write the desired page number to the
Page
register. The Page register is always at address
31 and is accessible from within any page.