Pin pitch is 0.05". So it is best suited to surface mount. It is more convenient to lay out PCB tracks so that they approach from both edges instead of interleaving them as is usually done for ATA/IDE connectors.
CF combines features from ISA bus, 16-bit PCMCIA, and ATA/IDE buses. It can appear as I/O mapped, memory mapped, or as an IDE device. The IDE mode is always 16-bit, but I/O and memory modes can present data as 8 or 16-bits. These features make it the most flexible choice, allowing it to be used by devices other than the PC - such as 8-bit processors in consumer electronics.
The memory-mapped mode occupies 1K of address space, the top half containing the selected page of data.
You can access all data on the card, through 8 or 16 bit data bus.
L = Low logic
H = High logic
NC = No Connection
NU = Not Used
D08-D15 required only for 16 bit access and not required when installed in 8-bit systems.
1. Devices should allow for 3-state signals not to consume current. 2. Should be grounded by the host. 3. Should be tied to VCC by the host. 4. Optional for CF+ Cards, required for CompactFlash Storage Cards.
"CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages"
This seems to give permission to wire CF cards into 5V systems. This would also be a wise design choice in the CF spec, because consumers avoid the hassle of making sure they have the "right voltage" card.
Sandisk"s design pagehas a freeware ATA Driver / FAT File System, and a circuit diagram for an IDE to CF adapter. The latter has no buffers, so it might be wise to avoid loading it with long drive cables.