Cirrus Logic CS4970x4 - Manual (Page 97)

7-4 Copyright 2013 Cirrus Logic, Inc. DS810UM6
Firmware Messaging
CS4953x4/CS4970x4 System Designer’s Guide
The 8-byte unsolicited read messages from the CS4953x4/CS4970x4 consist of a 4-byte read command
word which defines the type of unsolicited message and an associated 4-byte data word that contains
more information describing a system condition. The host senses that an unsolicited message is ready to
be read because the IRQ pin for the port being used goes low (SCP1_IRQ or PCP_IRQ). Every time the
existence of a message is detected, the host should read out the 8-byte unsolicited read message.
7.3.5 Index Configuration
Indices of the Firmware module can differ in properties that are important to the system firmware
programmer.
Indices NOT marked by a '†' must have their values configured before runtime, using the DSP Condenser
tool set. These register values will be loaded by the DSP auto-switching code. Indices marked by '†' may
have their values changed at runtime using host write commands.
7.3.6 Unsolicited Messages from DSP to the Host Microcontroller
There are times when the DSP needs to inform the host of certain changes during its operation. For
example, the DSP sending a message to the host indicating that the input stream has changed from
Dolby Digital to DTS. This information is useful to the host so it can update the Front panel of the Unit.
This type of message is an unsolicited message because it was initiated by the DSP rather than the host.
Changes that are reported to the host are:
• Changes in the input stream type reported by DSP_AUTODETECT_MSG
• Changes in the incoming bitstream reported by DSP_LAST_ACCN_MSG
7.3.7 DSP_AUTODETECT_MSG
1
The DSP_AUTODETECT_MSG is used to enable the DSP to notify the system host of changes in the
state of the DSP during run-time. A list of autodetect messages is shown in
Table 7-1 .
No Write Command.
No Read Request Command.
Unsolicited Read Response = 0x8100HHHH 0xhhhhhhhh
0xHHHH = index, 0xhhhhhhhh = data value
Unsolicited Read Command Word:
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9 8 7 6 5 4 3 2 1 0
OPCODE[31:16] INDEX[15:0]
Unsolicited Read Data Word:
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9 8 7 6 5 4 3 2 1 0
DATA WORD[31:0]
1. If auto-detect and other unsolicited messages are enabled, ensure that the system reads ALL the unsolicited messages from the
DSP before sending a write command to the DSP. This practice applies to the “boot-up” state as well as mode changes applied in
the DSP Manager. The auto-detect message identifies the stream type and the single or multi-word ACCN message. Failure to
read all unsolicited messages may result in no audio output from the DSP.