Hello, Guys:
I met the strange problem these days. I am using Philips p89c668 now. I want to use upper 128 bytes ram to be a buffer. before I used it, I wrote a small program to test the ram.. The strange problem occur.
1. 05H, Write to ram and read back. The phonemon is not only 05h is read back, but also other random values came back too.. it is very strange.

2.
11H, 91H
13H, 93H
I cann't save these numbers in the ram, even if I write the number to ram, I read back nothing.


3. All the other numbers are OK, except the numbers above.

buffer equ 80h

LCALL uart_init
mov r2, #00
mov r1, #00h
MOV R0, BUFFER
MYLOOPd:
mov a, r1
MOVX @R0,a
inc r1
INC R0
inc r2
CJNE r2, #100, MYLOOPd


MOV R2, #00h ;
MOV R0, BUFFER
MYLOOPC:
MOVX A, @R0
INC R0
MOV temp, A

LABEL:
MOV R1, #UART_LSR
MOVX A, @R1
ANL A, #40H ;TO SEE IF TRANS DATA EMPTY
MOV C, ACC.6 ;YES, SEND DATA AGAIN
JNC LABEL

MOV R1, #UART
MOV A, temp
MOVX @R1, A
inc R2
CJNE R2, #100, MYLOOPC


Anybody has idea?

Thanks.

Frank