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4.3 Card Boot
Basically the "card boot" operation boots MS-DOS from the ATA card, just like it is booted from a
floppy disk. For this terminal the boot operation looks the same as this case. However, this terminal
uses a boot process greatly different from a general card boot so that the MS-DOS in the drive C is
always loaded, in such a way that MS-DOS not residing in the card is booted.
Usually, in order to access the ATA card, a specific card driver is required. This card driver should
be registered as a MS-DOS block device for the MS-DOS and added as a new drive to the system.
Then the user can read from and write to the disk via the added drive by this device driver.
Fig. 4.5
However, in order to achieve a card boot, readout from the ATA card must be enabled before
MS-DOS is loaded into the main memory. To solve this conflict the terminal has a function in its
BIOS that can directly read the data from the ATA card. This function is assigned to the drive F (
drive E for models without an F-ROM) and the ATA card looks, from MS-DOS, like a physical
drive. As a result, when BIOS recognizes the presence of an ATA card during the boot process,
it will search for CONFIG.SYS and AUTOEXEC.BAT in the ATA card prior to loading MS-DOS.
If these files are found, the BIOS will load MS-DOS into main memory and shift control to
MS-DOS after designating the drive F as the current drive. Subsequently, MS-DOS will execute the
CONFIG.SYS and AUTOEXEC.BAT files in the current drive (drive F). This completes the load
process.
The mechanism determining which drive is specified as the one to be used by an application that
accesses the card is explained below. The drive G (drive F for models without F-ROM), which is a
drive specifically reserved for applications, will be enabled by CARDID.EXE which is loaded into
the main memory. It is loaded when CARDID.EXE is loaded and when both the drive F and drive G
are being enabled. If this is the case, note that if an attempt is made to access the drive F,
BIOS
G
CARD
Driver
ATA CARD
Physical
Drive
MS-DOS
Application