7782 Datasheet, PDF (15/63 Pages) STMicroelectronics – 32 Mbit (2Mb x 16, Dual Bank, Burst ) 1.8V Supply Flash Memory

M58CR032C, M58CR032D
Burst Configuration Register
The Burst Configuration Register is used to config-
ure the type of bus access that the memory will
perform.
The Burst Configuration Register is set through
the Command Interface. After a Reset or Power-
Up the device is configured for asynchronous
page read (M15 = 1) and the power save function
is disabled (M10 = 0). The Burst Configuration
Register bits are described in Table 4. They spec-
ify the selection of the burst length, burst type,
burst X latency and the Read operation. Refer to
Figures 7 and 8 for examples of synchronous burst
configurations.
Read Select Bit (M15). The Read Select bit,
M15, is used to switch between asynchronous and
synchronous Bus Read operations. When the
Read Select bit is set to ’1’, Bus Read operations
are asynchronous; when the Read Select but is
set to ’0’, Bus Read operations are synchronous.
Synchronous Burst Read is supported in both pa-
rameter and main blocks and can be performed
across banks.
On reset or power-up the Read Select bit is set
to’1’ for asynchronous access.
X-Latency Bits (M13-M11). The X-Latency bits
are used during Synchronous Bus Read opera-
tions to set the number of clock cycles between
the address being latched and the first data be-
coming available. For correct operation the X-La-
tency bits can only assume the values in Table 4,
Burst Configuration Register.
The correspondence between X-Latency settings
and the maximum sustainable frequency must be
calculated taking into account some system pa-
rameters.
Two conditions must be satisfied:
– (n + 1) t_K ≥ t_ACC - t_{AVK_CPU} + t_{QVK_CPU}
– t_K > t_KQV + t_{QVK_CPU}
where "n" is the chosen X-Latency configuration
code, t_K is the clock period, t_{AVK_CPU} is Clock to
Address Valid, L Low or E Low, whichever occurs
last, and t_{QVK_CPU} is the data setup time required
by the system CPU.
Power-Down Bit (M10). The Power-Down bit is
used to enable or disable the power-down func-
tion. When the Power-Down bit is set to ‘0’ (de-
fault) the power-down function is disabled. When
the Power-Down bit is set to ‘1’ power-down is en-
abled and the device goes into the power-down
state where the I_DD supply current is reduced to a
typical figure of I_DD2.
if this function is disabled the Reset/Power-Down,
RP, pin causes only a reset of the device and the
supply current is the standby value. The recovery
time after a Reset/Power-Down, RP, pulse is sig-
nificantly longer when power-down is enabled
(see Table 25).
Wait Bit (M8). In burst mode the Wait bit controls
the timing of the Wait output pin, WAIT. When the
Wait bit is ’0’ the Wait output pin is asserted during
the wait state. When the Wait bit is ’1’ (default) the
Wait output pin is asserted one clock cycle before
the wait state.
WAIT is asserted during a continuous burst and
also during a 4 or 8 burst length if no-wrap config-
uration is selected. WAIT is not asserted during
asynchronous reads, single synchronous reads or
during latency in synchronous reads.
Burst Type Bit (M7). The Burst Type bit is used
to configure the sequence of addresses read as
sequential or interleaved. When the Burst Type bit
is ’0’ the memory outputs from interleaved ad-
dresses; when the Burst Type bit is ’1’ (default) the
memory outputs from sequential addresses. See
Tables 5, Burst Type Definition, for the sequence
of addresses output from a given starting address
in each mode.
Valid Clock Edge Bit (M6). The Valid Clock
Edge bit, M6, is used to configure the active edge
of the Clock, K, during Synchronous Burst Read
operations. When the Valid Clock Edge bit is ’0’
the falling edge of the Clock is the active edge;
when the Valid Clock Edge bit is ’1’ the rising edge
of the Clock is active.
Wrap Burst Bit (M3). The burst reads can be
confined inside the 4 or 8 Double-Word boundary
(wrap) or overcome the boundary (no wrap). The
Wrap Burst bit is used to select between wrap and
no wrap. When the Wrap Burst bit is set to ‘0’ the
burst read wraps; when it is set to ‘1’ the burst read
does not wrap.
Burst length Bits (M2-M0). The Burst Length
bits set the number of Words to be output during a
Synchronous Burst Read operation; 4 words, 8
words or continuous burst, where all the words are
read sequentially.
In continuous burst mode the burst sequence can
cross bank boundaries.
In continuous burst mode or in 4, 8 words no-wrap,
depending on the starting address, the device ac-
tivates the WAIT output to indicate that a delay is
necessary before the data is output.
If the starting address is aligned to a 4 word
boundary no wait states are needed and the WAIT
output is not activated.
If the starting address is shifted by 1,2 or 3 posi-
tions from the four word boundary, WAIT will be
asserted for 1, 2 or 3 clock cycles when the burst
sequence crosses the first 64 word boundary, to
indicate that the device needs an internal delay to
read the successive words in the array. WAIT will
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