3 unsolicited message – Cirrus Logic AN333 User Manual
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AN333
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3.1 Communication Overview
provides the format of a solicited read message:
Figure 3-2. Read Command Data Word
provides the format of a solicited read message:
Figure 3-3. Read-Response Command and Read-response Data Words
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).
This type of message is considered an unsolicited message because it was initiated by the CS470xx rather than the host.
This message comes from the CS470xx to indicate a change in the system that must be addressed. The 8-byte unsolicited
read messages from the CS470xx consists 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. When the
IRQ pin for the port being used goes low (SCP1_IRQ or PCP_IRQ), the host senses that an unsolicited message is ready
to be read. Every time a message is detected, the host reads 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] (Bits 31:24 = Module ID+0x80, bits 23:20 =
0xc, bits 19:16 =
INDEX[15:0] (First index to be read)
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] (Bits 31:24= Module ID, Bits 23:20 =0xc,
Bits 19:16=
INDEX[15:0] (First index to be read)
Read-Response Data Word(s):
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]