Copyright(C) 1994 Terumasa KODAKA , Takeshi KOHNO


■INT 1Eh,1Fh: ROM BASIC entry/hot start resume entry

INT 1Eh (normal)
Classification
Name             N88 ROM BASIC entry/hot start resume entry
                 Undocumented
Target           Normal
Input
Output
Explanation    o INT 1Eh serves as both an N88 ROM BASIC entry and a hot start resume entry (reset while holding down [STOP]).
                 The main BIOS performs the following processing when the system starts up.
               o At a cold start (reset without holding down [STOP]), the INT 1Eh vector address is set to E800:0000h (N88 ROM BASIC startup entry).
                 At a hot start, the INT 1Eh vector address is not changed.
               o At a cold start, if there is a bootable device that meets the conditions specified in the memory switch, the OS starts up from that device.
                 At a hot start, no search for a bootable device is performed.
               o If "Use ROM BASIC" is selected in the System Setup menu, processing continues as follows.
               o If no bootable device is found on a cold start, or on a hot start, and DIP SW 2-1 is OFF, execute INT 1Eh.
                 If DIP SW 2-1 is ON, see the INT 1Fh (Normal) section.
               o On a cold start, INT 1Eh is set to E800:0000h, so N88 ROM BASIC starts.
                 On a hot start, in a DISK BASIC or ROM BASIC environment, a hot start resume entry is set in INT 1Eh, so the system restarts without clearing memory.
                 In an MS-DOS environment, INT 1Eh is set to FD80:27ECh. FD80:27ECh is a boot loader call entry
                 that boots from the device specified by the memory switch. Even if a hot start is performed, the OS is rebooted from the disk.
               o If it returns from INT 1Eh, boot from a bootable device.
Related


INT 1Eh (Hi-Res, LT/HA)
Classification
Name             Hot start resume entry
                 Undocumented
Target           Hi-Res, PC-98LT/HA
Input
Output
Explanation    o In Hi-Res mode and PC-98LT/HA, INT 1Eh is used as the resume entry during a hot start.
               o During a cold start, the vector address of INT 1Eh is set to the IRET routine in the BIOS.
               o During a hot start, the vector address of INT 1Eh is not changed.
                 The main BIOS executes INT 1Eh without searching for a bootable device.
               o During a hot start, if IRET is returned from INT 1Eh, the main BIOS performs boot processing from a bootable device in the same way as during a cold start.
Related


INT 1Fh (Normal)
Classification
Name             N80 ROM BASIC entry
                 Undocumented
Target           Normal (models that do not have a BIOS function in INT 1Fh)
Input
Output
Explanation    o INT 1Fh serves as both an N80 ROM BASIC entry and a restart entry during a hot start.
                 The main BIOS performs the following processing during system startup.
               o During a cold start, the INT 1Fh vector address is set to D800:2A00h (the N80 ROM BASIC startup entry).
                 During a hot start, the INT 1Fh vector address is not changed.
               o During a cold start, if there is a bootable device that meets the conditions specified in the memory switch, the OS will start from that device.
                 During a hot start, no search for a bootable device is performed.
               o If no bootable device is found on a cold start, or on a hot start, and DIP SW 2-1=ON, INT 1Fh is executed (if DIP SW 2-1=OFF, see the INT 1Eh section).
               o On a cold start, INT 1Fh is set to D800:2A00h, so if an N80 BASIC ROM is installed,
                 N80 ROM BASIC will start (if an N80 BASIC ROM is not installed, the system will run out of control).
                 On a hot start, in an N80 ROM BASIC environment, the hot start resume entry is set to INT 1Fh, so the system will restart without clearing memory.
               o Only the first generation PC-9801 officially supported N80 ROM BASIC.
Related