am42bds640ag Meet Spansion Inc., am42bds640ag Datasheet - Page 33

• Manufacturer Part Number: am42bds640ag
• Description: 64 Megabit 4 M ? 16-bit Cmos 1.8 Volt-only, Simultaneous Operation, Burst Mode Flash Memory And 16 Mbit 1 M ? 16-bit Static Ram Preliminary
• Manufacturer: Meet Spansion Inc.

RDY: Ready
The RDY is a dedicated output that, by default, indi-
cates (when at logic low) the system should wait 1
clock cycle before expecting the next word of data.
Using the RDY Configuration Command Sequence,
RDY can be set so that a logic low indicates the system
should wait 2 clock cycles before expecting valid data.
RDY functions only while reading data in burst mode.
The following conditions cause the RDY output to be
low: during the initial access (in burst mode), and after
the boundary that occurs every 64 words beginning
with the 64th address, 3Fh.
DQ6: Toggle Bit I
Toggle Bit I on DQ6 indicates whether an Embedded
Program or Erase algorithm is in progress or complete,
or whether the device has entered the Erase Suspend
mode. Toggle Bit I may be read at any address in the
same bank, and is valid after the rising edge of the final
WE# pulse in the command sequence (prior to the
program or erase operation), and during the sector
erase time-out.
During an Embedded Program or Erase algorithm
operation, successive read cycles to any address
cause DQ6 to toggle. When the operation is complete,
DQ6 stops toggling.
After an erase command sequence is written, if all
sectors selected for erasing are protected, DQ6
toggles for approximately 100 µs, then returns to
reading array data. If not all selected sectors are pro-
tected, the Embedded Erase algorithm erases the
unprotected sectors, and ignores the selected sectors
that are protected.
The system can use DQ6 and DQ2 together to deter-
mine whether a sector is actively erasing or is
erase-suspended. When the device is actively erasing
(that is, the Embedded Erase algorithm is in progress),
DQ6 toggles. When the device enters the Erase
Suspend mode, DQ6 stops toggling. However, the
system must also use DQ2 to determine which sectors
are erasing or erase-suspended. Alternatively, the
system can use DQ7 (see the subsection on DQ7:
Data# Polling).
If a program address falls within a protected sector,
DQ6 toggles for approximately 1 ms after the program
command sequence is written, then returns to reading
array data.
DQ6 also toggles during the erase-suspend-program
mode, and stops toggling once the Embedded
Program algorithm is complete.
See the following for additional information: Figure 4
(toggle bit flowchart), DQ6: Toggle Bit I (description),
F i g u r e 2 8 ,
32
“ To g g l e
B i t
P R E L I M I N A R Y
Ti m i n g s
Am42BDS640AG
(During Embedded Algorithm),” on page 57
timing diagram), and
tions,” on page
Note: The system should recheck the toggle bit even if DQ5
= “1” because the toggle bit may stop toggling as DQ5
changes to “1.” See the subsections on DQ6 and DQ2 for
more information.
DQ2: Toggle Bit II
The “Toggle Bit II” on DQ2, when used with DQ6, indi-
cates whether a particular sector is actively erasing
(that is, the Embedded Erase algorithm is in progress),
or whether that sector is erase-suspended. Toggle Bit
No
Figure 5. Toggle Bit Algorithm
Read Byte Twice
DQ6 = Toggle?
DQ6 = Toggle?
Adrdess = VA
Address = VA
Address = VA
33.
(DQ7–DQ0)
(DQ7–DQ0)
(DQ7–DQ0)
Read Byte
Read Byte
DQ5 = 1?
START
FAIL
Table 15, “DQ6 and DQ2 Indica-
Yes
Yes
Yes
No
No
November 1, 2002
PASS
(toggle bit