Campbell Scientific AM16/32B AM16/32B Relay Multiplexer - Page 17

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AM16/32B Relay Multiplexer 4.1.2 Clock 4.1.2.1 Mode A NOTE Pulsing the AM16/32B "CLK" line high ("RES" line already high) advances the channel. The voltage level must fall below 1.5 Vdc and then rise above 3.3 Vdc to clock the multiplexer. The AM16/32B operates in one of two clocking modes: Mode A-sequentially advances through each relay channel (as long as RESET is HI, relays are closed on each rising CLK edge). A more detailed description of Mode A is provided in Section 4.1.2.1, Mode A. Mode B-uses a relay address to go directly to a specific channel (see FIGURE 4-2). This reduces power consumption and wear on the relay switches. When multiple sensor types are connected to the AM16/32B, Mode B allows one sensor type to be measured more frequently than the other sensor types. A more detailed description of Mode B is provided in Section 4.1.2.2, Mode B. The AM16/32B detects a certain sequence on the RESET and CLK inputs to determine if it should operate in Mode A or Mode B; it does this every time the RESET line goes from LO to HI. The AM16/32B operates in Mode A under the following circumstances: • RESET HI for more than 9 ms. • A CLK pulse occurs while RESET is HI. When reset first goes high, the COM terminals (ODD H, ODD L and EVEN H, EVEN L) are disconnected from all sensor input terminals. When the first clock pulse arrives, the COM terminals are switched to connect with sensor input channel 1 (blue lettering) consisting of 1H, 1L, 2H, and 2L. When a second clock pulse arrives, the common lines are switched to connect to channel 2 (3H, 3L, 4H, 4L). The multiplexer advances on the leading edge of the positive going clock pulse. The CLK pulse should be at least 1 ms long. A delay (typically 10 to 20 ms) is inserted between the beginning of the CLK pulse and the measurement instruction to ensure sufficient settling time to relay contacts. 4.1.2.2 Mode B To go into Mode B, the RES line must be set HI for 5 ms (±1 ms) without any clocking; then, the RES line needs to be set LO. After the RESET has been set low, the AM16/32B counts the number of CLK pulses that occur before the RES line is activated again. This number is the relay address. After getting into Mode B, the rising edge of RESET (

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AM16/32B Relay Multiplexer
4.1.2 Clock
Pulsing the AM16/32B “CLK” line high (“RES” line already high) advances
the channel.
The voltage level must fall below 1.5 Vdc and then rise above 3.3
Vdc to clock the multiplexer.
The AM16/32B operates in one of two clocking modes:
Mode A—sequentially advances through each relay channel (as long as
RESET is HI, relays are closed on each rising CLK edge).
A more detailed
description of Mode A is provided in Section 4.1.2.1,
Mode A
.
Mode B—uses a relay address to go directly to a specific channel (see
FIGURE 4-2).
This reduces power consumption and wear on the relay
switches.
When multiple sensor types are connected to the AM16/32B, Mode
B allows one sensor type to be measured more frequently than the other sensor
types.
A more detailed description of Mode B is provided in Section 4.1.2.2,
Mode B
.
The AM16/32B detects a certain sequence on the RESET and CLK inputs to
determine if it should operate in Mode A or Mode B; it does this every time the
RESET line goes from LO to HI.
4.1.2.1 Mode A
The AM16/32B operates in Mode A under the following circumstances:
•
RESET HI for more than 9 ms.
•
A CLK pulse occurs while RESET is HI.
When reset first goes high, the COM terminals (ODD H, ODD L and EVEN H,
EVEN L) are disconnected from all sensor input terminals.
When the first
clock pulse arrives, the COM terminals are switched to connect with sensor
input channel 1 (blue lettering) consisting of 1H, 1L, 2H, and 2L.
When a
second clock pulse arrives, the common lines are switched to connect to
channel 2 (3H, 3L, 4H, 4L).
The multiplexer advances on the leading edge of
the positive going clock pulse.
The CLK pulse should be at least 1 ms long.
A delay (typically
10 to 20 ms) is inserted between the beginning of the CLK pulse
and the measurement instruction to ensure sufficient settling time
to relay contacts.
NOTE
4.1.2.2 Mode B
To go into Mode B, the RES line must be set HI for 5 ms (±1 ms) without any
clocking; then, the RES line needs to be set LO.
After the RESET has been set
low, the AM16/32B counts the number of CLK pulses that occur before the
RES line is activated again.
This number is the relay address.
After getting
into Mode B, the rising edge of RESET (<75 ms after last CLK pulse) activates
the addressed relay.
Once the addressed relay is activated, the AM16/32B
advances to the next relay with each CLK pulse (see FIGURE 4-2).
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