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W83977EF-AW Datasheet(PDF) 69 Page - Winbond |
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W83977EF-AW Datasheet(HTML) 69 Page - Winbond |
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69 / 142 page  W83977EF-AW/W83977EG-AW Publication Release Date: Apr. 2006 -67- Revision 1.2 7.3.15 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. 7.3.16 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. 7.4 Extension FDD Mode (EXTFDD) In this mode, W83977EF/EG 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) PinsDSKCHG#, RDATA#, WP#, TRAK0#, INDEX# will be logically ORed with pins PD4-PD0 to serve as input signals to the FDC. (3) Pins PD4-PD0 each will have an internal resistor of about 1K ohm to serve as pull-up resistor for FDD open drain/collector output. (4) If the parallel port is set to EXTFDD mode after the system has booted DOS or another operating system, a warm reset is needed to enable the system to recognize the extension floppy drive. 7.5 Extension 2FDD Mode (EXT2FDD) In this mode, W83977EF/EG 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 serve as input signals to the FDC. (3) Pins PD4-PD0 each will have an internal resistor of about 1K ohm to serve as pull-up resistor for FDD open drain/collector output. (4) If the parallel port is set to EXT2FDD mode after the system has booted DOS or another operating system, a warm reset is needed to enable the system to recognize the extension floppy drive. |
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