Cirrus Logic CS5378 - Manual (Page 30)

CS5378
DS639F3 30
9. CONFIGURATION BY MICROCONTROLLER
After reset, the CS5378 reads the state of the
GPIO7:BOOT pin to determine a source for con-
figuration commands. If BOOT is low, the CS5378
receives configuration commands from a micro-
controller.
9.1 Pin Descriptions
Pins required for microcontroller boot are listed
here, other serial pins are inactive.
SS:EECS - Pin 27
Slave select input pin, active low. Serial chip select
input from a microcontroller.
MOSI - Pin 26
Serial data input pin. Valid on rising edge of SCK,
transition on falling edge.
MISO - Pin 25
Serial data output pin. Valid on rising edge of
SCK, transition on falling edge. Open drain output
requiring a 10 k
Ω pull-up resistor.
SCK - Pin 24
Serial clock input pin. Serial clock input from mi-
crocontroller, maximum 4.096 MHz.
9.2 Microcontroller Hardware Interface
When booting from a microcontroller the CS5378
receives configuration commands and configura-
tion data through serial transactions, as shown in
Figure 18. 8-bit SPI opcodes and 8-bit addresses
are combined to read and write 24-bit configuration
commands and data.
Microcontroller serial transactions require toggling
the SS:EECS pin as the CS5378 chip select and
writing a serial clock to the SCK input. Serial data
is input to the CS5378 on the MOSI pin, and output
on the MISO pin.
9.3 Microcontroller Serial Transactions
Microcontroller configuration commands are writ-
ten to the digital filter through SPI registers. A 24-
bit command and two 24-bit data words can be
written to the SPI registers in any single serial
transaction. Some commands require additional
data words through additional serial transactions to
complete.
9.3.1 SPI opcodes
A microcontroller communicates with the CS5378
serial port using standard 8-bit SPI opcodes and an
8-bit address. The standard SPI ‘Read’ and ‘Write’
opcodes are listed in Figure 18.
SCK
MISO
MOSI Pin Logic
SPI
™
Figure 17. Serial Interface Block Diagram
Command
SS:EECS
Registers
Digital Filter
Interpreter
Serial