Cirrus Logic CS485xx - Manual (Page 27)

2-9 Copyright 2009 Cirrus Logic, Inc. DS734UM7
Softboot
CS485xxr Hardware User’s Manual
Figure 2-4. Soft Boot Sequence Flowchart
2.5.2.1 Softboot Steps
1. Send the SOFTBOOT message. The host sends the SOFTBOOT message to the CS485xx to begin
overlay swap.
2. Wait for IRQ low. The host then waits for SCP_IRQ to go low. If the TIMEOUT period has been
reached, the host should exit. If the IRQ pin is LOW, proceed to step 3.
3. Read the SOFTBOOT_ACK message. If the message is the SOFTBOOT_ACK message
(0x00000005), then the host should proceed to step 4. If the message is not the SOFTBOOT_ACK
message, the host should return to step 2.
4. Load Overlays. Repeat the boot procedure used to originally load the overlays into the CS485xx (i.e.
SLAVE_BOOT), but only the overlays that need to be swapped should be loaded. Skip the hard reset
sequence, starting the boot procedure from Step 2. Please note that this includes re-downloading all
hardware and software configurations for the
CS485xx overlays.
2.5.2.2 Softboot Example
Figure 2-5 is an example flow diagram and step-by-step description of the Softboot procedure based on the
SLAVE_BOOT procedure described earlier.
MSG == SOFTBOOT_ACK?
WRITE_* (SOFTBOOT)
READ_* (MSG) EXIT(ERROR)
N
Y
DONE
LOAD OVERLAYS
START
IRQ == LOW?
N
Y Y
N
TIMEOUT?