Cirrus Logic CS4953xx - Manual (Page 29)

2-15 Copyright 2010 Cirrus Logic, Inc. DS732UM10
Softboot
CS4953xx Hardware User’s Manual
2.5.2 Softboot Procedure
Figure 2-5 contains a flow diagram and description of the Softboot procedure. This is a step-by-step
guideline that can be used as an aid in developing the system controller code required to drive the
CS4953xx.
Figure 2-5. Soft Boot Sequence Flowchart
2.5.2.1 Softboot Procedure
1. Send the SOFTBOOT message. The host sends the SOFTBOOT message to the CS4953xx to
begin overlay swap.
2. Wait for IRQ low. The host then waits for SCP1_IRQ (or PCP_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 CS4953xx
(for example, SLAVE_BOOT, HCMB_<MODE>), 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 CS4953xx
overlays.
If no overlay, change as required, and go to Step 10, Section 2.5.2.3. .
MSG == SOFTBOOT_ACK?
WRITE_* (SOFTBOOT)
READ_* (MSG) EXIT(ERROR)
N
Y
DONE
LOAD OVERLAYS
START
IRQ == LOW?
N
Y Y
N
TIMEOUT?
GO TO STEP 10,
Section 2.5.2.3.