PC87373 Datasheet, PDF (140/174 Pages) National Semiconductor (TI) – LPC SuperI/O with Glue Functions

12.0 Legacy Functional Blocks
This chapter briefly describes the following blocks, which provide legacy device functions:
q _{Floppy Disk Controller (FDC)}
q _{Parallel Port (PP)}
q _{Serial Port1 and 2 (SP1 and SP2)}
q _{Keyboard and Mouse Controller (KBC)}
For details on the general implementation of each legacy block, see the SuperI/O Legacy Functional Blocks datasheet.
The register maps in this chapter use the following abbreviations for Type:
q _{R/W = Read/Write.}
q_R
= Read from register (write to the same address is to a different register).
q _{W = Write (see above).}
q _{RO = Read Only.}
q _{WO = Write Only. Reading from the bit returns 0.}
q _{R/W1C = Read/Write 1 to Clear. Writing 1 to a bit clears it to 0. Writing 0 has no effect.}
q _{R/W1S = Read/Write 1 to Set. Writing 1 to a bit sets its value to 1. Writing 0 has no effect.}
12.1 FLOPPY DISK CONTROLLER (FDC)
12.1.1 General Description
The generic FDC is a standard FDC with a digital data separator; it is software compatible with the µDP8473 and N82077.
The PC87373 FDC supports 14 of the 17 standard FDC signals described in the generic Floppy Disk Controller (FDC) chap-
ter, including:
• FDC supportS FM and MFM modes. 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 MSEN0 and MSEN1 signals is not supported.
• DRATE1 is not supported.
• DR1 is not supported.
• MTR1 is not supported.
Table 52 lists the FDC functional block registers. All registers are V_DD3 powered.
Table 52. FDC Register Map
Offset^{1 Mnemonic}
Register Name
00h
SRA Status A
01h
SRB Status B
02h
DOR Digital Output
03h
TDR Tape Drive
04h
MSR Main Status
DSR Data Rate Select
05h
FIFO Data (FIFO)
Type
RO
RO
R/W
R/W
R
W
R/W
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