Page 4.2
PROGRAMMABLE POTENTIOMETER MODULE 40-296
pickering
SECTION 4 - PROGRAMMING GUIDE
MODULE ARCHITECTURE
Figure 4.1 - 40-296 Potentiometer Module - Architecture of One Channel (8-Bit Version)
Resistor Chain B
1Ω
2Ω
4Ω 8Ω
16Ω 32Ω 64Ω
128Ω
Bit 1
Bit 2
Bit 3 Bit 4
Bit 5 Bit 6 Bit 7
Bit 8
Terminal B
Terminal A
Wiper
1Ω
2Ω
4Ω 8Ω
16Ω 32Ω 64Ω
128Ω
Bit 16
Bit 15
Bit 14 Bit 13
Bit 12 Bit 11 Bit 10
Bit 9
Resistor Chain A
The 40-296 Potentiometer Module is programmed using a sub-unit for each channel, with resistor chains A and B
being programmed individually. The relationship between the individual bits of each sub-unit and the corresponding
resistance value is show in Tables 4.1, 4.2, 4.3 and 4.4.
In order to make the module perform as a true potentiometer, resistor chains A and B have to be programmed
such that one is the complement of the other. For example: If bits 1 and 2 are set in resistor chain A, bits 9, 10, 11,
12, 13 and 14 have to be set in resistor chain B. This is outlined in Figure 4.2 and shown in the following program
examples.
The 8-bit version of the 40-296 Potentiometer Module is available with 5 or 9 separate channels which can be
programmed with values between 0Ω and 255Ω. 12-bit, 16-bit and 24-bit versions are also available which have
fewer channels and a greater resistance range - see the Specications section for details.
Each channel has two resistor chains A and B corresponding to the two sides of the potentiometer, with the common
point between the two chains corresponding to the wiper. In its default state, all relays are open, giving maximum
resistance on both sides of the potentiometer. The architecture of one channel of the 8-bit version is shown in Figure
4.1 below. Other versions with greater bit counts operate in basically the same way.
PROGRAMMING THE MODULE
Figure 4.2 - 40-296 Potentiometer Module - Setting The Resistance of One Channel
Resistor Chain B
1Ω
2Ω
4Ω 8Ω
16Ω 32Ω 64Ω
128Ω
Bit 1
Bit 2
Bit 3 Bit 4
Bit 5 Bit 6 Bit 7
Bit 8
Terminal B
Terminal A
Wiper
1Ω
2Ω
4Ω 8Ω
16Ω 32Ω 64Ω
128Ω
Bit 16
Bit 15
Bit 14 Bit 13
Bit 12 Bit 11 Bit 10
Bit 9
Resistor Chain A
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