W83977F-A Datasheet, PDF (103/182 Pages) Winbond – WINBOND I/O

W83977F-A/ W83977G-A/ W83977AF-A/ W83977AG-A
8.4 Extension FDD Mode (EXTFDD)
In this mode, the W83977F/ AF 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
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.
8.5 Extension 2FDD Mode (EXT2FDD)
In this mode, the W83977F/G, W83977AF/AG 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.
Publication Release Date: May 2006
-95 -
Revision 0.60