Table of Contents
Advertisement
T
S
3
2
M
~
1
G
C
F
T
S
3
2
M
~
1
G
C
F
T
S
3
2
M
~
1
G
C
F
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:
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.
Transcend Information Inc.
8
0
8
0
8
0
Table: Contiguous I/O Decoding
37
80X CompactFlash Card
V 1 . 1
Advertisement
Table of Contents
