
www.national.com
220
Revision1.2
P
10.0 Legacy Functional Blocks
This chapter briefly describes the following blocks, which provide legacy device functions:
G
Floppy Disk Controller (FDC).
G
Parallel Port (PP).
G
Serial Ports 1 and 2 (SP1 and SP2).
G
Keyboard and Mouse Controller (KBC).
The description of each Legacy block includes the sections listed below. For details on the general implementation of each
legacy block, see the
SuperI/O Legacy Functional Blocks
datasheet.
G
General Description.
G
Register Map table(s).
G
Bitmap table(s).
The register maps in this chapter use the following abbreviations for Type:
G
R/W
= Read/Write.
G
R
= Read from a specific register (write to the same address is to a different register).
G
W
= Write (see above).
G
RO
= Read Only.
G
WO
= Write Only. Reading from the bit returns 0.
G
R/W1C= Read/Write 1 to Clear. Writing 1 to a bit clears it to 0. Writing 0 has no effect.
G
R/W1S = Read/Write 1 to Set. Writing 1 to a bit sets its value to 1. Writing 0 has no effect.
10.1 FLOPPY DISK CONTROLLER (FDC)
10.1.1
The generic FDC is a standard FDC with a digital data separator and is DP8473 and N82077 software compatible. The PC8741x
FDC supports 14 of the 17 standard FDC signals described in the generic Floppy Disk Controller (FDC) chapter, including:
FM and MFM modes are supported. To select either mode, set bit 6 of the first command byte when writing to/reading
from a diskette, where:
—
0 = FM mode
—
1 = MFM mode
A logic 1 is returned during LPC I/O read cycles by all register bits, reflecting the state of floating (TRI-STATE) FDC pins.
Exceptions to standard FDC are:
Automatic media sense using the MSEN1 signal is not supported.
DRATE1 is not supported.
Table 59 lists the FDC functional block registers. All registers are V
DD
powered.
General Description
Table 59. FDC Registers
Offset
1
Mnemonic
Register Name
Type
00h
SRA
Status A
RO
01h
SRB
Status B
RO
02h
DOR
Digital Output
R/W
03h
TDR
Tape Drive
R/W
04h
MSR
Main Status
R
DSR
Data Rate Select
W
05h
FIFO
Data (FIFO)
R/W