AD1816 Analog Devices, AD1816 Datasheet - Page 41

• Manufacturer Part Number: AD1816
• Description: Single Chip Plug And Play Multimedia Audio Subsystem
• Manufacturer: Analog Devices

REV. A
PLUG AND PLAY KEY AND “ALTERNATE KEY” SEQUENCES
One additional feature of the AD1816A is an alternate programming method used, for example, if a BIOS wants to assume control
of the AD1816A and present DEVNODES to the OS (rather than having the device participate in Plug and Play enumeration). The
following technique may be used.
Instead of the normal 32 byte Plug and Play key sequence, an alternate 126 byte key is used. After the 126 byte key, the AD1816A
device will transition to the Plug and Play “sleep” state. It can then be programmed as usual using the standard Plug and Play ports.
After programming, the AD1816A should be sent to the Plug and Play “WFK” (wait for key) state. Once the AD1816A has seen the
alternate key, it will no longer parse for the Plug and Play key (and therefore never participate in Plug and Play enumeration). It can
be reprogrammed by reissuing the alternate key again.
Both the Plug and Play key and the alternate key are sequences of writes to the Plug and Play address register, 0x279. Below are the
ISA data values of both keys.
This is the standard Plug and Play sequence:
6a
b0
This is the longer, 126-byte alternate key. It is generated by the function:
f[n+1] = (f[n] >> 1)| (((f[n] ^ (f[n] >> 1)) & 0x01) << 6) f[0] = 0x01
01
28
68
7c
48
76
52
29
b5
58
40
14
34
3e
24
7b
69
54
da
2c
20
0a
1a
5f
12
3d
74
2a
ed
16
10
45
4d
2f
49
5e
3a
55
f6
8b
08
62
66
17
64
6f
5d
6a
fb
45
04
71
73
0b
32
37
6e
75
7d
a2
02
78
39
05
59
1b
77
7a
be
d1
41
3c
5c
42
6c
0d
3b
7d
–41–
df
e8
60
1e
2e
61
36
46
1d
7e
6f
74
30
4f
57
70
5b
63
4e
7f
37
3a
18
27
2b
38
2d
31
67
3f
1b
9d
0c
13
15
1c
56
58
33
1f
0d
ce
06
09
4a
0e
6b
2c
19
0f
86
e7
43
44
65
47
35
16
4c
07
AD1816A
c3
73
21
22
72
23
5a
4b
26
61
39
50
51
79
11
6d
25
53