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M58MR016C データシートの表示(PDF) - STMicroelectronics

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M58MR016C Datasheet PDF : 51 Pages
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M58MR016C, M58MR016D
figuration Register (A19-A16 are don’t care). At
Power-up the Read Configuration Register is set
to asynchronous Read mode, Power-down dis-
abled and bus invert (power save function) dis-
abled. A description of the effects of each
configuration bit is given in Table 14.
Read mode (CR15). The device supports an
asynchronous page mode and a synchronous
burst mode. In asynchronous page mode, the de-
fault at power-up, data is internally read and stored
in a buffer of 4 words selected by ADQ0 and ADQ1
address inputs. In synchronous burst mode, the
device latches the starting address and then out-
puts a sequence of data that depends on the Read
Configuration Register settings (see Figures 10,
11 and 12).
Synchronous burst mode is supported in both pa-
rameter and main blocks; it is also possible to per-
form burst mode read across the banks.
Bus Invert configuration (CR14). This register
bit is used to enable the BINV pin functionality.
BINV functionality depends upon configuration
bits CR14 and CR15 (see Table 14 for configura-
tion bits definition) as shown in Table 15. As output
pin BINV is active only when enabled (CR14 = 1)
in Read Array burst mode (CR15 = 0). As input pin
BINV is active only when enabled (CR14 = 1).
BINV is ignored when ADQ0-ADQ15 lines are
used as address inputs (addresses must not be in-
verted).
X-Latency (CR13-CR11). These configuration
bits define the number of clock cycles elapsing
from L going low to valid data available in burst
mode (see Figure 6). The correspondence be-
tween X-Latency settings and the maximum sus-
tainable frequency must be calculated taking into
account some system parameters.
Two conditions must be satisfied:
– (n + 2) tK tACC + tQVK_CPU + tAVK_CPU
– tK > tKQV + tQVK_CPU
where "n" is the chosen X-Latency configuration
code, tK is the clock period, tAVK_CPU is the ad-
dress setup time guaranteed by the system CPU,
and tQVK_CPU is the data setup time required by
the system CPU.
Power-down configuration (CR10). The RP pin
may be configured to give very low power con-
sumption when driven low (power-down state). In
power-down the ICC supply current is reduced to a
typical figure of ICC2; if this function is disabled
(default at power-up) the RP pin causes only a re-
set of the device and the supply current is the
stand-by value. The recovery time after a RP pulse
is significantly longer when power-down is en-
abled (see Table 31).
Wait configuration (CR8). In burst mode WAIT
indicates whether the data on the output bus are
valid or a wait state must be inserted. The config-
18/51
uration bit determines if WAIT will be asserted one
clock cycle before the wait state or during the wait
state (see Figure 7). WAIT is asserted during a
continuous burst and also during a 4 or 8 burst
length if no-wrap configuration is selected.
Burst order configuration (CR7) and Burst
Wrap configuration (CR3). See Table 16 for
burst order and length.
Clock configuration (CR6). In burst mode deter-
mines if address is latched and data is output on
the rising or falling edge of the clock.
Burst length (CR2-CR0). In burst mode deter-
mines the number of words output by the memory.
It is possible to have 4 words, 8 words or a contin-
uous burst mode, in which all the words are read
sequentially. In continuous burst mode the burst
sequence can cross the end of each of the two
banks (all banks in read array mode). In continu-
ous burst mode or in 4, 8 words no-wrap it may
happen that the memory will stop the data output
flow for a few clock cycles; this event is signaled by
WAIT going low until the output flow is resumed.
The initial address determines if the output delay
will occur as well as its duration. If the starting ad-
dress is aligned to a four words boundary no wait
states will be needed. If the starting address is
shifted by 1,2 or 3 positions from the four word
boundary, WAIT will be asserted for 1, 2 or 3 clock
cycles when the burst sequence is crossing the
first 64 word boundary. WAIT will be asserted only
once during a continuous burst access. See also
Table 16.

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