3 unsolicited message – Cirrus Logic AN298 User Manual
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AN298RC14
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3.1 Communication Overview
The following diagram provides shows the format of a solicited read message:
3.1.3
Unsolicited Message
The DSP needs to inform the host when the PLL is out of lock or there is a runtime memory allocation error (Malloc Failure).
Note that this type of message is an unsolicited message because it was initiated by the CS485xx rather than the host.
The PLL out of lock message is sent out on a best-efforts basis.
This message will come from the CS485xx to indicate a change in the system that must be addressed. The 8-byte
unsolicited read messages from the CS485xx 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.
Read Command Word:
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
OPCODE[31:16]
INDEX[15:0]
Read-Response Command Word:
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
OPCODE[31:16]
INDEX[15:0]
Read-Response Data Word:
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
DATA WORD[31:0]
Unsolicited Read Command Word:
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
OPCODE[31:16]
INDEX[15:0]
Unsolicited Read Data Word:
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
DATA WORD[31:0]