4 pins usb programming, what kind of section in electronics?

Brothers, please tell me a book or an article about the programming process and why I needed more than 4 pins, and 4 right now, and will do to program the MC, and the process as it occurs.
June 26th 19 at 14:22
2 answers
June 26th 19 at 14:24
Solution
Microcontrollers become more difficult - acquire integrated hardware implementations of interfaces, the separation of flash memory for the bootloader and the main program.

Now the microcontroller itself(the loader) pierces through the serial interface, was used almost video recording internal memory while programming in parallel the interface - hence the pile of wires.
and read useful info about the whole thing where possible? - Ewell commented on June 26th 19 at 14:27
Well, for example here microsin.net/programming/avr-working-with-usb/usb-... - Iliana_Strosi commented on June 26th 19 at 14:30
On some models it comes with from the factory - so if there is no marriage. - Iliana_Strosi commented on June 26th 19 at 14:36
June 26th 19 at 14:26
Solution
so it is possible and a conclusion to do.
reduction in signal lines complicates the internal logic of the programmer/debugger of. previously, the cost of the keys in the chip was a road, and therefore did not complicate the schemes is poor (the programmer used a couple of times during the entire life of the processor) nodes.
Now the cost of a penny, plus a tried and tested scheme, system, there are a bunch of waste of IP blocks and such. because put.
and about the programming process where it is possible to subtract to get the connection process and 4 contacts? - Ewell commented on June 26th 19 at 14:29
: it is right now its about Arduino and avr-s - Iliana_Strosi commented on June 26th 19 at 14:32
: read the documentation on the processor, the manufacturer usually has such a document, which is painted a Protocol programming and other things.
here is a description of the Protocol programming on "4 output" interface from Amtel, read.
www.atmel.com/images/atmel-0943-in-system-programm...

: It is possible to make the USB-bootloader in mask ROM formed in the production of crystal, then USB loading will work immediately. - Iliana_Strosi commented on June 26th 19 at 14:35

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