1 softboot steps, 2 softboot example – Cirrus Logic CS485xx User Manual

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2-9

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)

DONE

LOAD OVERLAYS

START

IRQ == LOW?

TIMEOUT?