I am working on a system using the CD4094BPWR CMOS shift register as a multiplexer / channel selector.
The shift register is supposed to select one channel at a time.
The system uses 5 boards in cascade, making a 40 bit shift register.
A master CPU clocks in data to enable the outputs, one at a time.
The trouble is that the outputs do not remain stable with the STROBE LOW, they should not change when STROBE is LOW!!
Scope Channel 1 is the STROBE (yellow)
Scope Channel 4 is the CLOCK (green)
Scope Channel 3 is the DATA (purple)
Scope Channel 2 is Q1 of the FIRST shift register in the cascade. (turquoise)
The scope image shows two bursts of 40 pulses, the first setting channel 1 LOW, followed by another burst setting channel 40 LOW.
Channel 2 ( output #1 ) should stay LOW for until the second STROBE pulse, but it goes HIGH after 2 more clocks!!!!???
Pulling my hair out trying to understand how this could be happening?
When the STROBE line is solidly LOW, there should be NO change in any output state!!!???
Googling around, I found one other reference to this problem, but no solutions.
I need 12 V logic output, so I cannot sub the CD74HC4094PWR.
The shift register is supposed to select one channel at a time.
The system uses 5 boards in cascade, making a 40 bit shift register.
A master CPU clocks in data to enable the outputs, one at a time.
The trouble is that the outputs do not remain stable with the STROBE LOW, they should not change when STROBE is LOW!!
Scope Channel 1 is the STROBE (yellow)
Scope Channel 4 is the CLOCK (green)
Scope Channel 3 is the DATA (purple)
Scope Channel 2 is Q1 of the FIRST shift register in the cascade. (turquoise)
The scope image shows two bursts of 40 pulses, the first setting channel 1 LOW, followed by another burst setting channel 40 LOW.
Channel 2 ( output #1 ) should stay LOW for until the second STROBE pulse, but it goes HIGH after 2 more clocks!!!!???
Pulling my hair out trying to understand how this could be happening?
When the STROBE line is solidly LOW, there should be NO change in any output state!!!???
Googling around, I found one other reference to this problem, but no solutions.
I need 12 V logic output, so I cannot sub the CD74HC4094PWR.
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