Contiguous I/O Mapped Addressing - SanDisk CompactFlash Extreme III Product Manual

ATA Register Set and Protocol
a. Register 0 is accessed with -CE1 low and -CE2 low (and A0 = Do not 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 off ­
set 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.
b. A byte access to register 0 with CE1 high and CE2 low accesses the error (read) or feature (write)
register.
4.2

Contiguous I/O Mapped Addressing

When the system decodes a contiguous block of I/O registers to select a CompactFlash
Memory Card, the registers are accessed in the block of I/O space decoded by the system as
follows:
Table 4-3
-REG
0
0
0
0
0
0
0
0
0
0
0
0
0
a. Register 0 is accessed with -CE1 low and -CE2 low (and A0 = Do not 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 off ­
set 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.
b. 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 regis­
ters are byte accessed in the order 9 then 8 the data will be transferred odd byte then even byte.
Repeated byte accesses to register 8 or 0 will access consecutive (even than odd) bytes from the
data buffer. Repeated word accesses to register 8, 9 or 0 will 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 will access consecutive (even then odd) bytes from the data
buffer. Byte accesses to register 9 access only the odd byte of the data.
02/07, Rev. 12.0
Contiguous I/O Decoding
A3 A2 A1 A0
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 1 0 1
1 1 1 0
1 1 1 1
4-2
SanDisk CompactFlash Card OEM Product Manual
Offset -IORD=0
0 a
Even RD Data
1 b
Error Register
2 Sector Count
3 Sector No.
4 Cylinder Low
5 Cylinder High
6 Select Card/Head
7 Status
8 b
Dup Even RD Data
9 b
Dup Odd RD Data
D b
Dup Error
E Alt Status
F Drive Address
© 2007 SanDisk Corporation
-IOWR=0
a
Even WR Data
b
Features
Sector Count
Sector No.
Cylinder Low
Cylinder High
Select Card/Head
Command
b
Dup Even WR Data
b
Dup Odd WR Data
b
Dup Features
Device Ctl
Reserved