read flash error why?

Action : Read Flash
Boot : SC8825/6825-EMMC
Tips:
1.Remove Battery, Insert usb cable, Insert battery
2.power off Phone, Remove & Reinsert Battery , insert USB Cable
(In Case Some Phone Required to hold bootkey)
Waiting for Phone Usb....
Phone found :
Connecting...
Bootstrap: SPRD3
Connected done.
sending 1st boot...
1st Boot is done.
Waiting for Boot init...
Done.
Switching Baudrate to 115200
Sending 2nd Boot...
2nd Boot done.
Waiting for Boot init...
Done.
SC Boot Ver : 8820
SC Boot Mode : 8820D000FFFFFFFF
Loading CST Boot image to RAM...
The CST Boot runs normally.
Reading CPU & Flash info...
CHIP : SC8825
CPU ID : 8820D000
EMMC ID : 1501004E3958524D42
EMMC Size: 1GB, usable capacity: 1.00GB
EMMC Name: eMMC_Samsung_N9XRMB
Boot Information completed.

Dumping Flash Image Now...
Error: failed to read buf.

Action completed
Time taken : 00:00:44
Reconnect Battery/USB Cable
CS-Tool Ver 1.60


model


txl-k501