Cirrus Logic CS485xx - Manual (Page 23)

2-5 Copyright 2009 Cirrus Logic, Inc. DS734UM7
Slave Boot Procedures
CS485xxr Hardware User’s Manual
2.3.2.1 Slave Boot Procedure
1. Toggle RESET. A download sequence is started when the host holds the RESET pin low for the
required time. The mode pins (HS[4:0]) must be in the appropriate state to set the host
communication mode before and immediately after the rising edge of RESET. Pull-up and pull-down
resistors are typically used to set the default state of the HS[4:0] pins.
2. Send the SLAVE_BOOT message. The host sends the SLAVE_BOOT message to the CS485xx
using the control port specified (serial port) and format specified (I
2
C, SPI, Intel, etc.) by the HS[4:0]
pins at reset.
3. Wait for IRQ low. The host then waits for SCP_IRQ to go low.
4. Read the BOOT_START message. If the initialization is successful, CS485xx sends out the
BOOT_START message and the host proceeds to step 5.
If initialization fails, the host must return to Step 1, and if failure is met again, the communication timing and
protocol should be inspected.
5. Send the ULD File. The host sends a.uld file to the CS485xx x.
6. Wait for IRQ low. The host then waits for SCP_IRQ to go low.
7. Read the BOOT_SUCCESS message. The host then reads a message from the appropriate
communications port. Each.ULD file contains a checksum that is compared at the end of the boot
process.
CS485xx sends a BOOT_SUCCESS message to the host if the checksum is correct after the
download.
If the checksum was incorrect, CS485xx responds with a BOOT_ERROR_CHECKSUM message. This
indicates that the image read by the DSP is corrupted. The communications interface hardware and code
image integrity should be checked if this occurs.
8. Repeat steps 2-7 for all code images/overlays. The host repeats these steps until all overlays for
the application have been successfully loaded. See the application note for more information on the
overlays necessary at start-up.
9. Send the SOFT_RESET message. After reading the BOOT_SUCCESS message on the last code
image/overlay, the host must send a SOFT_RESET message which will cause the application code to
begin executing.
10.Wait for IRQ low. The host then waits for SCP_IRQ to go low.
11.Read the APP_START message. If code execution is successful, the CS485xx sends out a
APP_START message. This indicates that the code has been initialized and can accept further
configuration messages. The host should not attempt further communication with the
CS485xx until the
APP_START message has been read.
If the CS485xx does not send an application start message, the host must return to Step 1.
12.Send Hardware Configuration messages. The slave boot procedure is completed. The operating
system on the CS485xx is now ready for host configuration of hardware and software.
Hardware configuration messages are used to define the behavior of the CS485xx ’s audio ports. A more
detailed description of the hardware configurations can be found in Section x of this manual.
13.Send Software Configuration messages.The software configuration messages are specific to each
application. The application code user’s guide for each application provides a list of all pertinent
configuration messages.
14.Send the KICKSTART message(s). The CS485xx application locks the PLL and begins processing
audio after receiving this message.