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T
T
T
S
S
S
3
3
3
2
2
2
M
M
M
~
~
~
1
1
1
G
G
G
C
C
C
F
F
F
8
8
8
0
0
0
80X CompactFlash Card
Transcend Information Inc.
37
5.2 Contiguous I/O Mapped Addressing
When the system decodes a contiguous block of I/O registers to select the CompactFlash Storage Card, the registers are
accessed in the block of I/O space decoded by the system as follows:
Table: Contiguous I/O Decoding
Notes:
1) Register 0 is accessed with -CE1 low and -CE2 low (and A0 = Don’t Care) as a word register on the combined Odd Data Bus and
Even Data Bus (D15-D0). This register may also be accessed by a pair of byte accesses to the offset 0 with -CE1 low and -CE2 high.
Note that the address space of this word register overlaps the address space of the Error and Feature byte-wide registers that lie at
offset
1. When accessed twice as byte register with -CE1 low, the first byte to be accessed is the even byte of the word and the second byte
accessed is the odd byte of the equivalent word access.
A byte access to register 0 with -CE1 high and -CE2 low accesses the error (read) or feature (write) register.
2) Registers at offset 8, 9 and D are non-overlapping duplicates of the registers at offset 0 and 1.
Register 8 is equivalent to register 0, while register 9 accesses the odd byte. Therefore, if the registers are byte accessed in the
order 9 then 8 the data shall be transferred odd byte then even byte.
Repeated byte accesses to register 8 or 0 shall access consecutive (even than odd) bytes from the data buffer. Repeated word
accesses to register 8, 9 or 0 shall access consecutive words from the data buffer. Repeated byte accesses to register 9 are not
supported. However, repeated alternating byte accesses to registers 8 then 9 shall access consecutive (even then odd) bytes from the
data buffer. Byte accesses to register 9 access only the odd byte of the data.
3) Address lines that are not indicated are ignored by the CompactFlash Storage Card for accessing all the registers in this table.