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This is incorrect, just read datasheet:
18LF4550 USB section needs 48MHz and can run at any voltage at 48MHz
CPU core can run at any speed it does not have to be 48MHz, you can select divide 96/6 or 96/4 instead of 96/2 and run at lower speed.
Will firmware work?
Not sure
But I will try this...
for 3.3V target devices only:
Did somebody try to lower whole clone voltage to 3.3V and use 18LF4550 and 16LF877A ?
I have bufferless version running for 5V devices, now moving to 3.3V and I am thinking to make a simple version that will run at 3.3v only.
This will eliminate buffer and high...
davemac2:
I had this issue once with one of ICD2s I made (SMD version published here on early pages of this topic). I did not find exactly what happenned but analyzing steps I did I am pretty sure I had the problem that you have.
ICD2 was OK on one PC and working fine for a day. Next morning I...
This does not make a sence. ACH126 used for 5V to 3 V and definately needed for PGC and PGD. I would expect ACHT125 to be only one.
Anyone can confirm?
Speaking of buffers to convert 5V signals to 3.3V:
Why PGC clock signal has bi-directional buffer?
I always thought that clock is coming from ICD2 so only one buffer 5->3.3V needed.
PGD is bi-directional signal that requires bi-directional buffer.
I am using my early design that is only 5V...
I never can understand why people pull very old threads and giving advices without reading thole thing and making offensive comments.
This issue been resolved long time ago.
gameoso
I found while ago with serial version MPLAB does not like any missing COM port numbers, so if you change COM5 to COM2 then it will work.
You have to do it in "advanced" com port properties.
fms,
Virtual com port created by FTDI driver does not have FIFO settings!
As far as I know, current FTDI driver does not work with ICD2 clone for some reason, you have to find old rev 2154 driver.
In original ICD2 RA3 pin monitors +13V line while RA1 monitoring Target Vcc
My version just supplies ~2.5V to these pins to make ICD2 firmware happy.
It would be better to monitor these voltages separately like real ICD2 does.
DG411 version is closer to real ICD2.
DG411 also has internal...
jajistenem
I think you are misunderstood 4550 power functionality:
VUSB pin 37 should always have 3.3V, it can't have 2.3V or 0, it must be 3.3V
With 5V power source, internal regulator must be enabled!
Here is what you should have
jajistenem:
Your schematics has 2 typical mistakes:
You powered 4550 from 3.3V source - this is incorrrect, it must be 5V, you can simply remove U11 and put a jumper IN-OUT
You connected VUSB power line to VUSB pin - this pin is output and required only a capacitor. I've seen 4550s damaged...
To all guys who claim unstable USB:
Do you have capacitor on VUSB pin (0.22-1uF) ?
Do you have anything else connected to this pin? - should be nothing.
Device will not be stable for sure if you are not using correct crystal.
USB must have exactly 6MHZ after all dividers and PLLs
I can't recall any stablity issue with many devices I built.
baudrate 19200 at89s51
I went over the code and found line loading TH1 with "FD"
I will post screenshot tonight.
Also I found that they are using delays with NOP instructions, so I will stay with 11.0592 crystal.
Using 11MHz was mistake and this explains unstable comms with large data...
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