M58LW032 STMICROELECTRONICS [STMicroelectronics], M58LW032 Datasheet - Page 16

• Manufacturer Part Number: M58LW032
• Description: 32 Mbit 2Mb x16, Uniform Block, Burst 3V Supply Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M58LW032A
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 bits are
described in Table 4. They specify the selection of
the burst length, burst type, burst X and Y laten-
cies and the Read operation. See figures 6 and 7
for examples of Synchronous Burst Read configu-
rations.
The Burst Configuration Register is set through
the Command Interface and will retain its informa-
tion until it is re-configured, the device is reset, or
the device goes into Reset/Power-Down mode.
The Burst Configuration Register is read using the
Read Electronic Signature Command at address
05h.
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.
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.
Internal Clock Divider Bit (M10). The
Clock Divider Bit is used to divide the internal clock
by two. When M10 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 M13-M11, and
the number of clock cycles between consecutive
reads will be twice the value set in M9. For exam-
ple 8-1-1-1 will become 16-2-2-2. When M10 is set
to ‘0’ the internal clock runs normally and the X
and Y-Latency values are those set in M13-M11
and M9.
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Internal
Y-Latency Bit (M9). The Y-Latency bit is used
during Synchronous Bus Read operations to set
the number of clock cycles between consecutive
reads. The Y-Latency value depends on both the
X-Latency value and the setting in M9.
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 Table 4,
Burst Configuration Register for valid combina-
tions of the Y-Latency, the X-Latency and the
Clock frequency.
Valid Data Ready Bit (M8). 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 (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’ the memory
outputs from sequential addresses. See Tables 5,
Burst Type Definition, for the sequence of ad-
dresses 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 opera-
tions. When the Valid Clock Edge bit is ’0’ the fall-
ing 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 (M2-M0). The Burst Length bits
set the maximum number of Words that can be
output during a Synchronous Burst Read opera-
tion.
Table 4, Burst Configuration Register gives the
valid combinations of the Burst Length bits that the
memory accepts; Tables 5, Burst Type Definition,
give the sequence of addresses output from a giv-
en starting address for each length.
M5 M4 and M3 are reserved for future use.
Valid
Data