14.2 Extended Channels (T7 Only) [T-Series Datasheet]

Overview - T7 Only

The T7 has 14 built-in analog inputs (AIN0 through AIN13). For applications that need more, up to 112 total external analog inputs can be utilized by multiplexing the built-in analog inputs. Each built-in analog channel may be multiplexed into 8 new channels, where the starting extended channel number is:

startingExtendedChannel = builtinChannel * 8 + 16

The extended channel range begins at AIN16.

When a built-in channel is multiplexed, the original channel number becomes unavailable.

For example, if AIN4 is multiplexed, AIN48 through AIN55 are exposed as usable AIN and AIN4 is no longer available.

Differential Channel Pairings

For differential channels in the extended range, a channel may be the positive channel if it is one of the following ranges:

AIN16 through AIN23
AIN32 through AIN39
AIN48 through AIN55
AIN64 through AIN71
AIN80 through AIN87
AIN96 through AIN103
AIN112 through AIN119

The negative channel is 8 higher than the positive channel. For example, the positive channel AIN48 is paired with AIN56 as the negative channel.

The differential channel pairs for the built-in AIN0 through AIN13 are adjacent even/odd pairs such that the positive channel is even and the negative channel is greater than the positive channel by 1. Since the built-in AIN are multiplexed as described above, an extended negative channel is 8 higher than its corresponding extended positive channel. For example, a valid differential extended channel pair would be a positive channel of AIN70 and AIN78 as the negative channel, since:

AIN70 maps to AIN6 and
AIN78 maps to AIN7.

For more information on differential extended channels, see the Mux80 Datasheet.

MIO

The DB37 connector has 3 MIO lines designed to address expansion multiplexer ICs (integrated circuits), allowing for up to 112 total external analog inputs. Whenever a read is done on analog input channel numbers 16 to 127, the T7 will automatically control the MIO lines to read the correct multiplexed AIN.

Mux80

The Mux80 accessory is used to multiplex AIN4 through AIN13, expanding them from 10 inputs to 80 inputs. AIN0 through AIN3 are still available (on the screw terminals of the T7). The extended channels can be read using the following registers. For further details, see the Mux80 Datasheet.

Note that when using the Mux80 board, the T7's MIO(0-2) lines are consumed for multiplexer signaling.

AIN Configurations on the Mux80

Use the following registers to configure AIN on the Mux80.

More details about single-ended vs differential are in the Single-ended or Differential section of the main AIN page.

More details about resolution are in the Resolution Index section of the main AIN page.

More details about range are in the Range / Gain section of the main AIN page.

More details about settling are in the Settling section of the main AIN page.

Custom Multiplexing Applications

Custom multiplexing and signal conditioning boards can be designed and automatically controlled by a T7 using the DG408 multiplexing IC from Intersil. The DG408 multiplexing IC from Intersil is the recommended multiplexer, and a convenient ±12 volt power supply is available on the DB37 so the multiplexers can pass bipolar signals (see Vm+/Vm- documentation in Section 16.0). These are the same ICs that do the device's internal channel multiplexing as well as the ICs integrated into the Mux80. Figure 14.2.1 shows the typical connections for a pair of multiplexers.

Figure 14.2.1 Typical DG408DVZ Multiplexer Connections.

Below is a table indicating the MIO states required for controlling 14 DG408 multiplexing ICs that each route to a single AIN line and the extended analog input channel that must be read for a single-ended signal to be measured correctly.

Output State			Expanded Channel Multiplexing Mapping
MIO0	MIO1	MIO2	AIN0	AIN1	AIN2	AIN3	AIN4	AIN5	AIN6	AIN7	AIN8	AIN9	AIN10	AIN11	AIN12	AIN13
0	0	0	16	24	32	40	48	56	64	72	80	88	96	104	112	120
1	0	0	17	25	33	41	49	57	65	73	81	89	97	105	113	121
0	1	0	18	26	34	42	50	58	66	74	82	90	98	106	114	122
1	1	0	19	27	35	43	51	59	67	75	83	91	99	107	115	123
0	0	1	20	28	36	44	52	60	68	76	84	92	100	108	116	124
1	0	1	21	29	37	45	53	61	69	77	85	93	101	109	117	125
0	1	1	22	30	38	46	54	62	70	78	86	94	102	110	118	126
1	1	1	23	31	39	47	55	63	71	79	87	95	103	111	119	127

More information about adding your own multiplexers can be found in Section 2.6.1 of the U6 Datasheet.

Differential Tables

The tables below show which channels are positive (Pos) or negative (Neg) when paired differentially. Additional information about using differential analog inputs with extended channels can be found in the Mux80 datasheet.

Built-in AIN (not multiplexed):

Pos	Neg
0	1
2	3
4	5
6	7
8	9
10	11
12	13

AIN0 and AIN1 (multiplexed with an external multiplexer):

Pos	Neg
16	24
17	25
18	26
19	27
20	28
21	29
22	30
23	31

AIN2 and AIN3 (multiplexed with an external multiplexer):

Pos	Neg
32	40
33	41
34	42
35	43
36	44
37	45
38	46
39	47

AIN4 and AIN5 multiplexed with the Mux80 (or an external multiplexer):

Pos	Neg
48	56
49	57
50	58
51	59
52	60
53	61
54	62
55	63

AIN6 and AIN7 multiplexed with the Mux80 (or an external multiplexer):

Pos	Neg
64	72
65	73
66	74
67	75
68	76
69	77
70	78
71	79

AIN8 and AIN9 multiplexed with the Mux80 (or an external multiplexer):

Pos	Neg
80	88
81	89
82	90
83	91
84	92
85	93
86	94
87	95

AIN10 and AIN11 multiplexed with the Mux80 (or an external multiplexer):

Pos	Neg
96	104
97	105
98	106
99	107
100	108
101	109
102	110
103	111

AIN12 and AIN13 multiplexed with the Mux80 (or an external multiplexer):

Pos	Neg
112	120
113	121
114	122
115	123
116	124
117	125
118	126
119	127