James, There are a series of schematics on paper. I haven't put anything=20 into a schematic program yet. Before I complete a section the schematic=20 is in flux as I try new ideas. Once the section is finished then I=20 finalize the schematic. Eventually it will all be put into a program.=20 Yes, this is kind of backwards but I prefer the feel and texture of=20 paper. It is also less painful for me. The display board is 4 dual 3/4 inch high 7 segment LEDs that are=20 driven by 8 CD4511 BCD to 7 segment drivers. Not only are the BCD pins=20 brought out, all of the control pins are also brought out. This gives me=20 maximum flexibility in wiring the display board. The board that you see=20 below the display board is just a test fixture that will be disassembled=20 when I am finished. There are 4 74LS390 divide by ten decimal to BCD counters on a=20 second board. These chips are the actual frequency counters. All of the=20 control pins are again individually pulled high or low so as to put the=20 chips into a known and working state. So I can then pull the _clr pins=20 low to reset the counters to zero. Again this gives me maximum=20 flexibility. More wire, resistors, and connections but resistors are=20 cheap and the wire is almost free. The reason I say that the wire is almost free is because I will go=20 to Goodwill or some place like them and buy a 25 foot parallel printer=20 cable. I then cut the ends off and open the cable up. I now have several=20 hundred feet of 22 gauge wire of various colors that is perfect for=20 carrying the control signals between the different chips. I usually only=20 pay about $5 for the cable. Before I thought of using the PIC I was driving a 74HCT4060 with a=20 20MHz crystal. By making the crystal osc adjustable and forcing the osc=20 to run at 20.48MHz I can use the Q11 output on the 4060. This gives me=20 5KHz. I can then divide this by five. I now have a 1KHz signal that I=20 can divide by ten 3 times I now have a 1 Hz signal. I can also pick off=20 10 Hz, 5Hz, and make 2Hz with another counter connected to the 10Hz=20 output. This is five divide by ten counters which is two 74LS390 chips=20 and a 74LS90. I also had a couple of 74lLS4053 multiplexers that allowed=20 me to select which frequency was going to be used for the gating and the=20 reset signals. This is where my inexperience bit me. I knew that I needed some=20 monostable multivibrators to control the length of the gating signal and=20 to control the reset pulse. I just couldn't get past this. I then=20 thought of using the PIC. It is pretty easy to setup to provide=20 different frequencies and different pulse widths. So the PIC is the TB=20 control, display length control, and selects the proper DP. The front end is a common emitter amplifier. I'm using a 2n4401 NPN=20 transistor with a broadband filter on the input. The input is also=20 signal strength limited by two diodes. This protects the front end from=20 a large signal input. The signal from the collector of this amp is then=20 fed to a 74HCT14 schmitt trigger inverter. The input is connected=20 through a 10K multiturn pot. You adjust this to give the best output=20 shape with a very low input of about 20mV. I'm also going to put in a=20 divide by ten prescaler on the front end. This will allow the counter to=20 go to 100MHz. I won't be able to use a 7490 or 74390 as these will only=20 go up to 50MHz. When the prescaler is selected the PIC will position the=20 DP in the correct place. The output of this inverter then goes to the input of a 74HC132=20 NAND gate. This is where the gating signal from the PIC comes into play.=20 The NAND gate is opened by the signal from the PIC for what ever length=20 of time that has been set by a rotary switch or a set of push buttons.=20 The output of the NAND gate goes to the first counter in the first=20 74LS390 chip. The signal then ripples through the 74LS390s. I can also use the PIC to blank out the high digits that aren't=20 needed and to control the latch on the the CD4511s so that there is no=20 ripple effect. Personally I like to see the digits run up as the signal=20 comes in and I don't mind the leading zeros. A little power could be=20 saved by blanking the leading zeros. If this was a commercial product I=20 would probably put in a couple of switches that would allow the operator=20 to choose blanking or no blanking and ripple or latching. I'm not yet set on which PIC I want to use. The 684 doesn't have=20 enough pins to do everything that I want to do. I can use some=20 multiplexers to give me more inputs and outputs with fewer pins but this=20 makes the circuit more complex. It also makes the program more complex. I'm thinking of moving the program over to a 690. By the time I set=20 the 684 up I have 9 I/O pins. The 690 will have 13 I/O pins. This is=20 quite a difference. I have already started working on porting the=20 program to the 690. I have it where it will compile but I'm not certain=20 that I have set up the CCP pins for Digital I/O. Well that is where I'm at. The switches and the pot to control the=20 TB and the display time are not hooked up yet. So the values for these=20 times are hardwired. So is the DP. When I am done these will be able to=20 be controlled from the front panel. As you can see it runs and it is=20 reasonably accurate. This is with a resonator that is running at=20 3.797MHz instead of a crystal running at 20MHz. Even though the 684s are supposed to be able to run at 20MHz. I=20 must have a very early one. It is marked -4 after the part number so it=20 is only rated to 4MHz and it won't run at 20MHz. I tried to set it up=20 for the 8MHz internal frequency and I get a compile error that that=20 feature is not supported. I have a few newer 684s on the way. they will=20 be here sometime next week. I have now built three prototyping boards for PICs. One board for=20 84s, a board for 62xs, and a board for the 684s. This board also has=20 jumpers on it so that I can use several 14 and 18 pin PICs in it. These=20 boards have a 18 pin ZIF socket, pull up resistors that can be=20 disconnected by way of switches, sockets for crystals or resonators, and=20 a 18 pin 90 degree connector that allows the board to be plugged in to a=20 breadboard. You can see this board in the picture that shows the meters=20 on the power supply. The green ZIF socket is clearly visible. Thanks, rich! On 7/25/2014 8:21 PM, James Cameron wrote: > On Fri, Jul 25, 2014 at 07:53:42PM -0500, Richard R. Pope wrote: >> https://farm3.staticflickr.com/2912/14558909297_e21b214d19_m.jpg >> https://farm4.staticflickr.com/3862/14558723419_82f0dc5e8a_m.jpg >> https://farm6.staticflickr.com/5581/14558909927_e1fe032d81_m.jpg >> https://farm3.staticflickr.com/2903/14765227683_594200b1d0_m.jpg --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .