I am planning on using this chip but im not sure what the clock pin is for. The data sheet for it can be found here
This is a serial loading device. It controls 34 LEDs by reading in a 35bit serial word. Its non-standard, so you will have to know something about serial communication. The clock signal latches in each data bit. The 35bit serial word is a '1' follwed by 34 bits that signify which LEDs get turned on or off. Without a clock signal, the 35bit data wont get locked in. You have a couple of choices: Use the parallel port. Use a microcontroller with custom code for transmitting a 35bit serial word. This is not standard serial transffer. Using an RS232 driver wont work, since it only transffers 8bit data words. The datasheet gives a good explanation of the clock and data timings. It runs upto 500kHz, but you can have much lower speeds so handling this chip will not be a problem timing wise. The problem is with creating a custom serial transfer.
im still a little confused, so i need to send a bit down the clock everytime i send a bit through the data?
No, you just need to have a clock that's running at the same frequency as the serial transfer. If you're generating the serial bits with another IC, it should have a clock as well, and you can just tie the two together. Serial transfer works by having each bit last only for a certain time period. For the sake of the argument, let's have a .001s bit length. Now, if you were to send 5 1s in a row, then there'd be a period where the serial transfer would be in a HIGH state for .005s, 5 bit lengths. The driver needs to know how long each bit is so it interpret the data correctly. An incorrect clock at the driver means that either bits will get skipped over (clock too slow) or read more than once (clock too fast).
ah, I see, so if i was unable to find another IC that can make it easier to send the 35 bits, and had to connect it directly to the serial port, i would set the clock to the baud rate of the port?
