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400X CompactFlash Card
Transcend Information Inc.
V1.0
58
Card (Drive) Address Register (Address 3F7h[377h]; Offset Fh)
This register is provided for compatibility with the AT disk drive interface. It is recommended that this register not
be mapped into the host’s I/O space because of potential conflicts on Bit 7.
Bit 7: this bit is unknown.
Implementation Note:
Conflicts may occur on the host data bus when this bit is provided by a Floppy Disk Controller operating at
the same addresses as the CompactFlash Storage Card. Following are some possible solutions to this
problem for the PCMCIA implementation:
1) Locate the CompactFlash Storage Card at a non-conflicting address, i.e. Secondary address (377) or
in an independently decoded Address Space when a Floppy Disk Controller is located at the Primary
addresses.
2) Do not install a Floppy and a CompactFlash Storage Card in the system at the same time.
3) Implement a socket adapter that can be programmed to (conditionally) tri-state D7 of I/0 address
3F7h/377h when a CompactFlash Storage Card is installed and conversely to tristate D6-D0 of I/O
address 3F7h/377h when a floppy controller is installed.
4) Do not use the CompactFlash Storage Card’s Drive Address register. This may be accomplished by
either a) If possible, program the host adapter to enable only I/O addresses 1F0h-1F7h, 3F6h (or
170h-177h, 176h) to the CompactFlash Storage Card or b) if provided use an additional Primary /
Secondary configuration in the CompactFlash Storage Card which does not respond to accesses to
I/O locations 3F7h and 377h. With either of these implementations, the host software shall not attempt
to use information in the Drive Address Register.
Bit 6 (-WTG): this bit is 0 when a write operation is in progress; otherwise, it is 1.
Bit 5 (-HS3): this bit is the negation of bit 3 in the Drive/Head register.
Bit 4 (-HS2): this bit is the negation of bit 2 in the Drive/Head register.
Bit 3 (-HS1): this bit is the negation of bit 1 in the Drive/Head register.
Bit 2 (-HS0): this bit is the negation of bit 0 in the Drive/Head register.
Bit 1 (-nDS1): this bit is 0 when drive 1 is active and selected.
Bit 0 (-nDS0): this bit is 0 when the drive 0 is active and selected.