M48Z2M1Y, M48Z2M1V Operation modes
Doc ID 5135 Rev 6 7/20
2 Operation modes
The M48Z2M1Y/V has its own power-fail detect circuit. The control circuitry constantly
monitors the single 5 V supply for an out of tolerance condition. When V
CC
is out of
tolerance, the circuit write protects the SRAM, providing a high degree of data security in the
midst of unpredictable system operations brought on by low V
CC
. As V
CC
falls below
approximately 3 V, the control circuitry connects the batteries which sustain data until valid
power returns.
Table 2. Operating modes
Note: X = V
IH
or V
IL
; V
SO
= battery backup switchover voltage.
2.1 READ mode
The M48Z2M1Y/V is in the READ mode whenever W (WRITE enable) is high and E (chip
enable) is low. The device architecture allows ripple-through access of data from eight of
16,777,216 locations in the static storage array. Thus, the unique address specified by the
21 address inputs defines which one of the 2,097,152 bytes of data is to be accessed. Valid
data will be available at the data I/O pins within address access time (t
AVQV
) after the last
address input signal is stable, providing that the E
(chip enable) and G (output enable)
access times are also satisfied. If the E
and G access times are not met, valid data will be
available after the later of chip enable access time (t
ELQV
) or output enable access time
(t
GLQV
). The state of the eight three-state data I/O signals is controlled by E and G. If the
outputs are activated before t
AVQV
, the data lines will be driven to an indeterminate state
until t
AVQV
. If the address inputs are changed while E and G remain low, output data will
remain valid for output data hold time (t
AXQX
) but will go indeterminate until the next address
access.
Figure 4. Address controlled, READ mode AC waveforms
Note: Chip enable (E
) and output enable (G) = low, WRITE enable (W) = high.
Mode V
CC
E G W
DQ0-
DQ7
Power
Deselect
3.0 to 3.6 V
or
4.5 to 5.5 V
V
IH
X X High Z Standby
WRITE V
IL
XV
IL
D
IN
Active
READ V
IL
V
IL
V
IH
D
OUT
Active
READ V
IL
V
IH
V
IH
High Z Active
Deselect V
SO
to V
PFD
(min)
(1)
1. See Table 10 on page 15 for details.
X X X High Z CMOS standby
Deselect ≤ V
SO
(1)
X X X High Z Battery backup mode
AI02051
tAXQX
DATA VALID
A0-A20
DQ0-DQ7
tAVAV
tAVQV
Obsolete Product(s) - Obsolete Product(s)
