- Sat Jun 05, 2010 7:41 pm
#102472
Hello everyone! Finally got around to register on the Sparkfun forum.
So I recently obtained a 74h595 shift register and am a little puzzled about the clock pins. Why is there two of them!?
What is the difference between the shift register clock input and the storage register clock input? I am not using a microcontroller, instead I am just wiring the parallel outputs (Q0 - Q7) to a 7-segment display (through resistors of course) and just wanted to clock it on my own by tapping a N/O tactile switch. Both clock pins are tied to ground through a 10K resistor. I attached two separate N/O switches to +5V and the other side to the respective clock pin so when I want like to clock a bit in, all I would do is just pulse it HIGH by briefly pressing the switch. But when I try to do this, either all of the LEDs go on or all of them go off. SOOOOO that is why I need a little help understanding how exactly the two clock pins work. In my ECE class, we only discussed FFs and other ICs with only one clock pin so I am a little stuck. Here is a list of my connections and data sheet:
Data sheet: http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf
My pin connections:
pin 1 - Q1 -- connected to a segment
pin 2 - Q2 -- connected to a segment
pin 3 - Q3 -- connected to a segment
pin 4 - Q4 -- connected to a segment
pin 5 - Q5 -- connected to a segment
pin 6 - Q6 -- connected to a segment
pin 7 - Q7 -- connected to a segment
pin 8 - Gnd -- connected to ground
pin 9 - Q7'(serial output) -- not connected
pin 10 - MR (bar) -- connected to +5V
pin 11 - SH_CP -- grounded through a 10K resistor until tapped with +5V
pin 12 - ST_CP -- grounded through a 10K resistor until tapped with +5V
pin 13 - OE (bar) connected to ground
pin 14 - DS -- connected to +5V or ground
pin 15 - Q0 -- connected to a segment
pin 16 - Vcc -- connected to +5V
So I recently obtained a 74h595 shift register and am a little puzzled about the clock pins. Why is there two of them!?
What is the difference between the shift register clock input and the storage register clock input? I am not using a microcontroller, instead I am just wiring the parallel outputs (Q0 - Q7) to a 7-segment display (through resistors of course) and just wanted to clock it on my own by tapping a N/O tactile switch. Both clock pins are tied to ground through a 10K resistor. I attached two separate N/O switches to +5V and the other side to the respective clock pin so when I want like to clock a bit in, all I would do is just pulse it HIGH by briefly pressing the switch. But when I try to do this, either all of the LEDs go on or all of them go off. SOOOOO that is why I need a little help understanding how exactly the two clock pins work. In my ECE class, we only discussed FFs and other ICs with only one clock pin so I am a little stuck. Here is a list of my connections and data sheet:
Data sheet: http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf
My pin connections:
pin 1 - Q1 -- connected to a segment
pin 2 - Q2 -- connected to a segment
pin 3 - Q3 -- connected to a segment
pin 4 - Q4 -- connected to a segment
pin 5 - Q5 -- connected to a segment
pin 6 - Q6 -- connected to a segment
pin 7 - Q7 -- connected to a segment
pin 8 - Gnd -- connected to ground
pin 9 - Q7'(serial output) -- not connected
pin 10 - MR (bar) -- connected to +5V
pin 11 - SH_CP -- grounded through a 10K resistor until tapped with +5V
pin 12 - ST_CP -- grounded through a 10K resistor until tapped with +5V
pin 13 - OE (bar) connected to ground
pin 14 - DS -- connected to +5V or ground
pin 15 - Q0 -- connected to a segment
pin 16 - Vcc -- connected to +5V