w83977atg Winbond Electronics Corp America, w83977atg Datasheet - Page 105

• Manufacturer Part Number: w83977atg
• Description: W83877tf Plus Kbc, Gp I/o, Wake-up, Fir, Cir, Pb-free
• Manufacturer: Winbond Electronics Corp America

8.3.15 DMA Transfers
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.
8.3.16 Programmed I/O (NON-DMA) Mode
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.
8.4
In this mode, W83977ATF/ATG 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 8-1.
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
8.5
In this mode, W83977ATF/ATG 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
Table8-1.
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
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.
Extension FDD Mode (EXTFDD)
Extension 2FDD Mode (EXT2FDD)
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W83977ATF/W83977ATG
Publication Release Date: May 2006
Revision 0.6