ttl problem on tiny6410

I made a small device that could connect with TTL port.
My device has EM-18 cart reader module, that can read data from RFID card.
When I connected it to TINY6410 TTL port and opened serial port terminal
application on tiny6410 ,selected each comm port (ttySAC0-1-2-3) then press
connect button and pass the RFID card but nothing happened.(but the led
buzzer is show the read card is working) 

( I also should say my device is working on mini2440 and shows card data on
serial port terminal application on mini2440)

I'd start by checking in /dev to see which ttySAC_ are present on both the
mini2440 and TINY6410

Hello @devef. really nice to meet you my friend.
Yes, you sat right. when the ttl was connected these ttys were present.
----------------------------------------------------------------------
[root@FriendlyARM /]# dmesg | grep tty
Kernel command line: root=/dev/mtdblock2 rootfstype=yaffs2 init=/linuxrc
console=ttySAC0,115200
console [ttySAC0] enabled
s3c6400-uart.0: ttySAC0 at MMIO 0x7f005000 (irq = 16) is a S3C6400/10
s3c6400-uart.1: ttySAC1 at MMIO 0x7f005400 (irq = 20) is a S3C6400/10
s3c6400-uart.2: ttySAC2 at MMIO 0x7f005800 (irq = 24) is a S3C6400/10
s3c6400-uart.3: ttySAC3 at MMIO 0x7f005c00 (irq = 28) is a S3C6400/10
USB Serial support registered for Garmin GPS usb/tty
usbcore: registered new interface driver ipwtty
ipw: v0.4:IPWireless tty driver
---------------------------------------------------------------------
all ttl devices are connected. but none of them get data from serial port
ttl.

Maybe ttySAC1,2 and 3 are not enabled.  ttySAC0 is for the console terminal
display.

I suspect you have to enable the tty you want to connect to in the kernel. 
It has been years since I played with this stuff.  Maybe, try searching for
<ttySAC1 enable> on this site.

Good luck!

thanks devef. I found it. the pdf of tiny6410 say the ttl pin like the
picture. but when i make loop-back to pin number 1 and 2. the system reset.
the i put my loop-back to pin number 3 and 4 ( as the picture they should
be gcc and vcc) but they are TX and RX. just this . 

thanks my friend :)