Specifications

Theory of Operation
EPC-100 Hardware Reference 4-12
Address Block Name Notes
03F0-03F1h Configuration Write only
1,2
03F0-03F1h Floppy Disk Read only
2
03F2-03F5h, 03F7h Floppy Disk
2
03F8-03FFh Serial Port, COM1
2
02F8-02FFh Serial Port, COM2
2
0278-027Ah Parallel Port, LPT1
2
01F0-01F7h, 03F6h, 03F7h IDE (not used) AT Mode
2,3
Table 4-4. Super I/O Chip Address Blocks.
Notes:
1
Configuration registers can only be modified by writing a security code sequence
to 3F0h. The configuration registers can only be read in configuration mode by
accessing 3F1h. Access to status registers A and B of the floppy disk is disabled
in configuration mode. Outside of configuration mode, a read of 3F0h accesses
status register A and a read of 3F1h accesses status register B of the floppy disk.
2
Default address. These addresses can be changed in configuration setup.
3
Addresses 320-323h and 3F5-3F7h for XT Mode. This is selected in
configuration setup.
This Super I/O chip only decodes the I/O address space with the 10 LSBs.
Additional circuitry gates the address enable with the upper six bits of the I/O address
range (which must be all zero to allow AEN to pass.) The ECP registers located 778-
77Ah are also decoded and allowed to pass to the Super I/O chip. Therefore, the
address of the chip is decoded to 16 bits, with the top six expected to be zero.
RS-232 Ports
The RS-232 ports are standard PC COM serial ports based on the 16550 architecture.
COM A is normally mapped to I/O address 3F8h-3FFh and uses interrupt IRQ4. If
not needed, COM B can be disabled in the BIOS Setup Integrated Peripherals Sub-
Menu to free up the I/O address and interrupt for usage by other expansion products.
COM B is mapped to I/O address 2F8h-2FFh and uses interrupt IRQ3.