Background: recently in the home made a 51 minimum system board on STC 51 chip (use), and then download circuit using the isp download, use the downloader, hold and STC - isp downloader are not, but it has been showed detection equipment, and the isp download line, I buy is going to give avrmega16 single chip microcomputer to download, but see written on taobao, 51 can also use, so welding an isp interface, on the hole hole board,
Question:
Line 1: the isp download has been testing equipment, is to detect a serial port in use at, or serial port being used, the problem is?
2: baidu see some myself, say on STC with ats c51, 51 c52 series are used in a serial port to download, and at s51, 52 is the usb - isp download, but their asked taobao, common to all isp download line 51, reply, at the same time, I see a general in the single chip microcomputer is used on STC 51 chip, also have the isp download module,
The question is: the isp download line can only be at s51, s52, avr with? Hold in STC 51 above there is no way to use? If I want to use your isp download, so I need to change the at chip?
3: there is now bought a usb to TTL (not to), there is a question that usb to TTL and isp download have what distinction, I observed their connection position is different, the isp is P1, and connecting usb to TTL is TXD, and RXD, at the same time both to use download chip seems different, isp USES mega8, and there is a the rest of the usb to TTL chips,

Two more: after just now and checked the usbasp only supports the avr and at89s series, and for 8951 series is not supported on STC, is that right? Hold on STC needs using STC - isp download?