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The boot loader can also be executed by holding PSEN LOW, EA greater than VIH (such as +5 V), and ALE HIGH (or not connected)
at the falling edge of RESET.
yes, but p89c669 can not work,p89v51 work

I have download the user manual and datasheet of p89c669, but have't found any special specification about ISP

what's the different?

I have bought two chip P89v51rb2 and p89c669.
P89v51 can be download programs by flashmagic software,but the P89c669 can't.
when the chips are power on when haven't been programmed, I found the RxD and Txd is 5v on p89v51. The RXD0 is 5v on p89c669,but the TxD0 is 0v, while RXD1 and TXD1 is 5v. the ALE is 1.7V and can measured pulse signal,so the crystal is work.
what should I do?