PARALLEL PORT FLOPPY DISK CONTROLLER
The Floppy Disk Control signals are available
2. Control Register read as "cable not
connected" STROBE, AUTOFD and SLC = 0
and nINIT =1
3. Status Register reads: nBUSY = 0, PE = 0,
SLCT = 0, nACK = 1, nERR = 1
optionally on the parallel port pins. When this
mode is selected, the parallel port is not available.
There are two modes of operation, PPFD1 and
PPFD2. These modes can be selected in the
Parallel Port Mode Register, as defined in the
Parallel Port Mode Register, Logical Device 3, at
0xF1. PPFD1 has only drive 1 on the parallel port
pins; PPFD2 has drive 0 and 1 on the parallel port
pins.
The following FDC pins are all in the high
impedence state when the PPFDC is actually
selected by the drive select register:
1. nWDATA, DENSEL, nHDSEL, nWGATE,
nDIR, nSTEP, nDS1, nDS0, nMTR0, nMTR1.
When the PPFDC is selected the following pins
are set as follows:
2. If PPFDx is selected, then the parallel port
can not be used as a parallel port until
"Normal" mode is selected.
1. nPDACK: high-Z
2. PDRQ: not ECP = high-Z, ECP & dmaEn = 0,
ECP & not dmaEn = high-Z
3. PINTR: not active, this is hi-Z or Low
depending on settings.
The FDC signals are muxed onto the Parallel Port
pins as shown in Table 42.
Note: nPDACK, PDRQ and PINTR refer to the
nDACK, DRQ and IRQ chosen for the parallel
port.
For ACPI compliance the FDD pins that are
multiplexed onto the Parallel Port function
independently of the state of the Parallel Port
controller. For example, if the FDC is enabled
onto the Parallel Port the multiplexed FDD
interface functions normally regardless of the
Parallel Port Power control, CR22.3. Table 41
illustrates this functionality.
The following parallel port pins are read as follows
by a read of the parallel port register:
1. Data Register (read) = last Data Register
(write)
TABLE 45 - PARALLEL PORT FDD CONTROL
PARALLEL PORT FDC PARALLEL PORT
CONTROL FDC STATE
PARALLEL
PARALLEL PORT
STATE
PORT
POWER
CR22.3
LD3:CRF1.1
LD3:CRF1.0
1
0
X
0
0
1
X
0
0
X
1
OFF
OFF
ON
ON
OFF
OFF
(NOTE1)
NOTE1: The Parallel Port Control register reads as “Cable Not Connected” when the Parallel Port FDC
is enabled; i.e., STROBE = AUTOFD = SLC = 0 and nINIT = 1.
107
SMSC [ SMSC CORPORATION ]
