m58lw064c STMicroelectronics, m58lw064c Datasheet - Page 16

• Manufacturer Part Number: m58lw064c
• Description: 64 Mbit 4mb X16, Uniform Block, Burst 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

M58LW064C
CONFIGURATION REGISTER
The Configuration Register is used to configure
the type of bus access that the memory will per-
form. The Configuration Register bits are de-
scribed in Table 3. They specify the selection of
the burst length, burst type, burst X and Y laten-
cies and the read operation. See figures
for examples of Synchronous Burst Read configu-
rations.
The Configuration Register is set through the
Command Interface and will retain its information
until it is re-configured, the device is reset, or the
device goes into Reset/Power-Down mode. The
Configuration Register is read using the Read
Electronic Signature Command at address 05h.
Read Select Bit (CR15). The Read Select bit,
CR15, is used to switch between asynchronous
and synchronous read operations. When the Read
Select bit is set to ’1’, read operations are asyn-
chronous; when the Read Select but is set to ’0’,
read operations are synchronous.
On reset or power-up the Read Select bit is set to
’1’ for asynchronous access.
X-Latency Bits (CR13-CR11). The
bits are used during Synchronous read operations
to set the number of clock cycles between the ad-
dress being latched and the first data becoming
available. For correct operation the X-Latency bits
can
3., Configuration
Internal Clock Divider Bit (CR10). The Internal
Clock Divider Bit is used to divide the internal clock
by two. When CR10 is set to ‘1’ the internal clock
is divided by two, which effectively means that the
X and Y-Latency values are multiplied by two, that
is the number of clock cycles between the address
being latched and the first data becoming avail-
able will be twice the value set in CR13-CR11, and
the number of clock cycles between consecutive
reads will be twice the value set in CR9. For exam-
ple 8-1-1-1 will become 16-2-2-2. When CR10 is
set to ‘0’ the internal clock runs normally and the X
and Y-Latency values are those set in CR13-CR11
and CR9.
Y-Latency Bit (CR9). The Y-Latency bit is used
during synchronous read operations to set the
16/61
only
assume
Register.
the
values
X-Latency
in
6
and
Table
7
number of clock cycles between consecutive
reads. The Y-Latency value depends on both the
X-Latency value and the setting in CR9.
When the Y-Latency is 1 the data changes each
clock cycle; when the Y-Latency is 2 the data
changes every second clock cycle. See
3., Configuration Register
of the Y-Latency, the X-Latency and the Clock fre-
quency.
Valid Data Ready Bit (CR8). The
Ready bit controls the timing of the Valid Data
Ready output pin, R. When the Valid Data Ready
bit is ’0’ the Valid Data Ready output pin is driven
Low for the active clock edge when invalid data is
output on the bus. When the Valid Data Ready bit
is ’1’ the Valid Data Ready output pin is driven Low
one clock cycle prior to invalid data being output
on the bus.
Burst Type Bit (CR7). 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’ the memory
outputs from sequential addresses. See
4., Burst Type
dresses output from a given starting address in
each mode.
Valid Clock Edge Bit (CR6). The
Edge bit, CR6, 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.
Burst Length Bit (CR2-CR0). The Burst Length
bits set the maximum number of Words that can
be output during a Synchronous Burst Read oper-
ation.
Table 3., Configuration Register
combinations of the Burst Length bits that the
memory accepts;
give the sequence of addresses output from a giv-
en starting address for each length.
CR5, CR4 and CR3 are reserved for future use.
Definition, for the sequence of ad-
Table 4., Burst Type
for valid combinations
gives the valid
Valid
Valid
Definition,
Table
Table
Clock
Data