Cirrus Logic CS4953xx - Manual (Page 28)

Softboot
CS4953xx Hardware User’s Manual
DS732UM10 Copyright 2010 Cirrus Logic, Inc 2-14
2.5 Softboot
The O/S application code for the CS4953xx allows users to swap out one or more overlays during run
time, without the need for re-download of the entire overlay stack. This is helpful for reducing the time
required for switching between different types of incoming audio data streams.
The Softboot procedure includes initial messaging that sends the CS4953xx into a boot state where the
host can boot the CS4953xx with different overlays according to the boot methods outlined in this chapter.
This includes a soft reset of the CS4953xx, which then requires that the host send or re-send the
hardware and software configuration messages.
2.5.1 Softboot Messaging
Two messages are relevant to the softboot procedure for the CS4953xx. These messages are:
SOFTBOOT and SOFTBOOT_ACK.
The SOFTBOOT message is sent from the host controller to the CS4953xx to indicate to the CS4953xx
that the system requires swapping of overlays.
The SOFTBOOT_ACK is sent from the CS4953xx to the host controller to indicate that the host can now
boot the CS4953xx with the new overlays.
Table 2-10. SOFTBOOT Message
Mnemonic Value
SOFTBOOT
0x81000009
0x00000001
Table 2-11. SOFTBOOT_ACK Message
Mnemonic Value
SOFTBOOT_ACK 0x00000005