w83977atf Winbond Electronics Corp America, w83977atf Datasheet - Page 202

• Manufacturer Part Number: w83977atf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

DMA transfers are always to or from the ecpDFifo, tFifo, or CFifo. The DMA uses the standard PC
DMA services. The ECP requests DMA transfers from the host by activating the PDRQ pin. The DMA
will empty or fill the FIFO using the appropriate direction and mode. When the terminal count in the
DMA controller is reached, an interrupt is generated and serviceIntr is asserted, which will disable the
DMA.
The ECP or parallel port FIFOs can also be operated using interrupt driven programmed I/O.
Programmed I/O transfers are to the ecpDFifo at 400H and ecpAFifo at 000H or from the ecpDFifo
located at 400H, or to/from the tFifo at 400H. The host must set the direction, state, dmaEn = 0 and
serviceIntr = 0 in the programmed I/O transfers.
The ECP requests programmed I/O transfers from the host by activating the IRQ pin. The
programmed I/O will empty or fill the FIFO using the appropriate direction and mode.
In this mode, the W83977ATF changes the printer interface pins to FDC input/output pins, allowing
the user to install a second floppy disk drive (FDD B) through the DB-25 printer connector. The pin
assignments for the FDC input/output pins are shown in Table 5-1.
After the printer interface is set to EXTFDD mode, the following occur:
(1) Pins MOB and DSB will be forced to inactive state.
(2) Pins DSKCHG, RDATA , WP, TRAK0, INDEX will be logically ORed with pins PD4-PD0 to serve
(3) Pins PD4-PD0 each will have an internal resistor of about 1K ohm to serve as pull-up resistor for
(4) If the parallel port is set to EXTFDD mode after the system has booted DOS or another operating
In this mode, the W83977ATF changes the printer interface pins to FDC input/output pins, allowing
the user to install two external floppy disk drives through the DB-25 printer connector to replace
internal floppy disk drives A and B. The pin assignments for the FDC input/output pins are shown in
Table5-1.
After the printer interface is set to EXTFDD mode, the following occur:
(1) Pins MOA , DSA , MOB, and DSB will be forced to inactive state.
(2) Pins DSKCHG, RDATA , WP, TRAK0, and INDEX will be logically ORed with pins PD4-PD0 to
(3) Pins PD4-PD0 each will have an internal resistor of about 1K ohm to serve as pull-up resistor for
(4) If the parallel port is set to EXT2FDD mode after the system has booted DOS or another operating
5.3.15 DMA Transfers
5.3.16 Programmed I/O (NON-DMA) Mode
5.4 Extension FDD Mode (EXTFDD)
5.5 Extension 2FDD Mode (EXT2FDD)
as input signals to the FDC.
FDD open drain/collector output.
system, a warm reset is needed to enable the system to recognize the extension floppy drive.
serve as input signals to the FDC.
FDD open drain/collector output.
system, a warm reset is needed to enable the system to recognize the extension floppy drive.
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Publication Release Date:April 1998
W83977ATF
PRELIMINARY
Revision 0.52