SanDisk SDP3B - I;O Transfer Function; I;O Function

SDP3B FlashDisk Product Manual
SanDisk SDP3B FlashDisk Product Manual © 1998 SANDISK CORPORATION 43
4.5 I/O Transfer Function
4.5.1 I/O Function
The I/O transfer to or from the SDP3B FlashDisk
can be either 8 or 16 bits. When a 16-bit accessible
port is addressed, the signal -IOIS16 is asserted
by the SDP3B FlashDisk. Otherwise, the -IOIS16
signal is de-asserted. When a 16 bit transfer is
attempted, and the -IOIS16 signal is not asserted
by the SDP3B FlashDisk, the system must
generate a pair of 8-bit references to access the
word‘s even byte and odd byte. The SDP3B
FlashDisk permits both 8- and 16-bit accesses to
all of its I/O addresses, so -IOIS16 is asserted for
all addresses to which the SDP3B FlashDisk
responds.
The SDP3B FlashDisk may request the host to
extend the length of an input cycle until data is
ready by asserting the -WAIT signal at the start
of the cycle.
Table 4-15 I/O Function
Function Code -REG -CE2 -CE1 A0 -IORD -IOWR D15-D8 D7-D0
Standby Mode X H H X X X High Z High Z
Byte Input Access
(8 bits)
L
L
H
H
L
L
L
H
L
L
H
H
High Z
High Z
Even-Byte
Odd-Byte
Byte Output Access
(8 bits)
L
L
H
H
L
L
L
H
H
H
L
L
Don’t Care
Don’t Care
Even-Byte
Odd-Byte
Word Input Access
(16 bits)
L L L L L H Odd-Byte Even-Byte
Word Output Access
(16 bits)
L L L L H L Odd-Byte Even-Byte
I/O Read Inhibit H X X X L H Don’t Care Don’t Care
I/O Write Inhibit H X X X H L High Z High Z
High Byte Input Only
(8 bits)
L L H X L H Odd-Byte High Z
High Byte Output Only
(8 bits)
L L H X H L Odd-Byte Don’t Care