Hello there!

I was working on the P89c51rd2HP ckt. which was designed by Harsha and I downloaded from his home page. After powering up the circuit, I accessed ISP features and performed the Blank check and erased couple of memory blocks etc. I Switched off the power and when switched On again, everything was gone. I tried all the possibilities but no way. I replaced the Chip, it started working but after switching off when I switched ON .It was gone with the wind......

Can any one help me out to trace out the fault ? I feel there is something wrong with the reset ckt.

If someone has better simple schematic diagram for P89c51rd2HP which
works without problem.

The existing ckt. is connected as follows:
MCU P89C51rd2 Connections
-RST (Pin 9) connected to +5V through 1uf, 8K2 connected to gnd
-Rxd (Pin 10)-HIN232CP TxD (Pin12)
-TxD (Pin 11)-HIN232CP TxD (Pin11)
-Crystal 11.0592MHZ connected across XTAL2 & XTAL1 with 1 uf - GND
-GND (Pin 20 ) to Ground
-Vcc (Pin 40) - +5V through 1uF
-EA(Pin31),ALE(Pin30),P2.7(Pin28),P2.6(Pin27) connected to +5V thr 10K each.
-PSEN (Pin 29)-gnd thr 10K.

Serial Interface HIN232CP Connections
-1uf across Pins 1,3 & 4,5
-R1 out (Pin12)-MCU TxD
-T1 In (Pin11)-MCU RxD
-Pin 16 - +5V thr 1uF-gnd
-Pin15 directly ro gnd
-Pin 6 - 1uF - gnd and RS232 DB9 pin 5
-T1 out (14) - DB9 (pin 2 Rx)
-R1 In (13) - DB9 (pin 3 Tx)


Regards

Harnam