Floppy Disk Controller; General; Drive Formats; Video Controllers - Mitsubishi Electric LS Pro Hardware Technical Reference

Video controllers

The video controllers implement all the control and data registers, and all the data
manipulation capabilities and data paths of the standard VGA controller. In addition
they can generate high-resolution display modes (those supported in BIOS are
listed in the table above), and uses several enhancements to improve on the
performance of the standard VGA implementation.
These enhancements include a pair of FIFOs. One isolates the processor from
display memory, allowing zero wait state writes from processor to display
memory, provided the FIFO is not full. Reads also occur with zero wait states
provided the data required is held in the FIFO. The second allows the use of
fast page mode cycles to fetch data from display memory, increasing the time
that the display memory is available for processor accesses.
In addition the GD5426 includes a hardware BitBLT which accelerates video
performance under GUIs.
3.6

FLOPPY DISK CONTROLLER

General

The diskette drive controller fitted on the system board is an Intel 82077 chip.
This single chip provides a complete IBM compatible floppy disk controller,
including data separator, on a single chip.
The controller has several internal registers which are accessible by the system
microprocessor. These registers, and their usage, are described in detail in
section 5. An illustration and pinout of the floppy drive connector are given at
the rear of this section.

Drive formats

The controller supports:
• two drives
• 500 kbyte unformatted media, 360 kbyte formatted
• 1 Mbyte unformatted media, 720 kbyte formatted
• 1.66 Mbyte unformatted media, 1.2 Mbyte formatted
• 2 Mbyte unformatted media, 1.44 Mbyte formatted
• supports 250, 300 and 500 kbits/sec transfer rates
• programmable precompensation delay
In this implementation a single 1.44 Mbyte floppy drive can be fitted. 720k and
1.44M diskettes are supported for both single and multithread operations. The
default precompensation is 125 nanoseconds and is present for all cylinders.
System Board
LS PRO HARDWARE TECHNICAL REFERENCE 3/15