Cirrus Logic CS485xx - Manual (Page 26)

Softboot
CS485xxr Hardware User’s Manual
DS734UM7 Copyright 2009 Cirrus Logic, Inc. 2-8
2.5 Softboot
The O/S application code for the CS485xx 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 CS485xx into a boot state where the host
can boot the CS485xx with different overlays according to the boot methods described in this chapter. This
includes a soft reset of the CS485xx , 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 CS485xx . These messages are: SOFTBOOT
and SOFTBOOT_ACK.
The SOFTBOOT message is sent from the host controller to the CS485xx to indicate to the CS485xx that the
system requires swapping of overlays.
The SOFTBOOT_ACK is sent from the CS485xx to the host controller to indicate that the host can now boot
the CS485xx with the new overlays.
2.5.2 Softboot Procedure
Figure 2-4 describes 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 CS485xx .
Table 2-6. SOFTBOOT Message
Mnemonic Value
SOFTBOOT
0x81000009
0x00000001
Table 2-7. SOFTBOOT_ACK Message
Mnemonic Value
SOFTBOOT_ACK 0x00000005