PARALLEL PORT FLOPPY DISK CONTROLLER
2. Control Register read as "cable not
The Floppy Disk Control signals are available
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.
connected" STROBE, AUTOFD and SLC =
0 and nINIT =1
3. Status Register reads: nBUSY = 0, PE = 0,
SLCT = 0, nACK = 1, nERR = 1
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 must 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 should function 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 41 - MODIFIED PARALLEL PORT FDD CONTROL
PARALLEL PORT FDC PARALLEL PORT PARALLEL PORT
CONTROL FDC STATE
PARALLEL
PORT POWER
STATE
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.
104
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