Configuration Register
M58LT256JST, M58LT256JSB
6
Configuration Register
The Configuration Register configures the type of bus access that the memory performs.
Refer to Section 7 for details on read operations.
The Configuration Register is set through the command interface using the Set
Configuration Register command. After a reset or power-up the device is configured for
asynchronous read (CR15 = 1). The Configuration Register bits are described in Table 11
The bits specify the selection of the burst length, burst type, burst X latency and the read
operation. Refer to Figures 5 and 6 for examples of synchronous burst configurations.
6.1
6.2
Read select bit (CR15)
The read select bit, CR15, switches between asynchronous and synchronous read
operations.
When the read select bit is set to ’1’, read operations are asynchronous. When the read
select bit is set to ’0’, read operations are synchronous.
Synchronous burst read is supported in both parameter 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 (CR13-CR11)
The X latency bits are used during synchronous read operations to set the number of clock
cycles between the address being latched and the first data becoming available. Refer to
Figure 5: X latency and data output configuration example.
For correct operation the X latency bits can only assume the values in Table 11:
Configuration Register.
Table 10 shows how to set the X latency parameter, taking into account the speed class of
the device and the frequency used to read the Flash memory in synchronous mode.
Table 10. X latency settings
fmax
tKmin
X latency min
30 MHz
40 MHz
52 MHz
33 ns
25 ns
19 ns
3
4
5
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NUMONYX [ NUMONYX B.V ]
