Ts-7400 Recovery; Bootup Process; Loading Or Transferring Files; Transferring Files Via The Ethernet Port - Technologic Systems TS-7400 Hardware & Software Installation

TS-7400 Recovery

Although it is easy to get your board into an unbootable state during development if you
botch a modification, it is equally easy to use the TS-9441 to recover the default startup.
To do so, place the "Boot" jumper on the TS-9441 and reset the board. In approximately
3 seconds, the board will have fastbooted to the TS-9441 flash and presented a shell
prompt. To recover the default initrd and linuxrc, enter the command "save", remove the
Boot jumper, and reboot back to a restored to factory default TS-7400.

2.3 Bootup Process

The processor first runs code from the dedicated EEPROM chip containing the TS-
FLASHBOOT bootup program. TS-FLASHBOOT sets up bus timing, SDRAM, and other
low-level hardware initialization. It also loads sector 0 from the NAND flash chip at 0x1000
physical address. Once its loaded, it jumps (in ARM Thumb mode) to the first instruction,
with register r0 containing a function pointer to a routine to read sectors from the boot
media (NAND flash) and in r1 a routine to a function to print a character string to the serial
port. The routines have the following C signature:
void read(unsigned int sector, unsigned char *buf, unsigned int
nsectors)
void puts(unsigned char *buf)
By default, whats contained in sector 0 of the NAND flash is a DOS-style partition table at
offset 446 and a 446 byte Linux-specific kernel bootloader at offset 0.
bootloader contains code to parse the partition table looking for 2 partitions marked with
partition ID '0xda'. It uses the start sector and size parameters of the partition table to
load the first partition (Linux kernel) at offset 0x2180000 and the second partition (if it
exists) at 0x1000000 (Linux initrd). If a bad sector or a sector failing an ECC check is
detected, it skips to the next 16kbyte boundary and continues-- in this way, NAND chips
with bad sectors remain bootable. Next, it composes up the necessary pre-boot ATAG
data structures required by Linux kernels and jumps to address 0x2180000 at which point
the Linux kernel takes over.
One of the first things the Linux kernel does is disable the hardware watchdog. The
watchdog is armed for 8 second expiry before automatic reboot and will be constantly fed
as long as the firmware or MBR Linux bootloader is reading from flash. The board will
appear to constantly reboot every 8 seconds should something go wrong. The TS-7400
uses an external watchdog implemented in the CPLD instead of the CPU internal
watchdog to guarantee proper reset operation in the case of a severely malfunctioning
CPU. The CPU internal watchdog is also available, but Technologic Systems does not
recommend using it.

2.4 Loading or Transferring Files

Three methods are available for transferring files between a desktop PC and your TS-
7400: Ethernet downloads, flash memory devices, and Zmodem downloads. Full
descriptions of each are detailed below. Other programs that use serial ports to transfer
should work as well.

Transferring Files via the Ethernet Port

The default JFFS Linux root file system includes a small FTP server that can be used for
uploading/downloading of files across an Ethernet network. Simply point your preferred
FTP client to your TS-7400 IP address (default is 192.168.0.50). You can login as root or
any valid user previously created from the useradd utility. By default, the JFFS image will
not accept anonymous FTP.
© May, 2010
TS-7400/TS-9441 MANUAL
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