M58LT128GS datasheet(16/98 Pages) STMICROELECTRONICS

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3 Bus operations

M58LT128GST, M58LT128GSB

16/98

Bus operations

There are six standard bus operations that control the device. These are Bus Read, Bus Write,

Address Latch, Output Disable, Standby and Reset. See Table 3: Bus Operations, for a

summary.

Typically glitches of less than 5ns on Chip Enable or Write Enable are ignored by the memory

and do not affect Bus Write operations.

3.1

Bus Read

Bus Read operations are used to output the contents of the Memory Array, the Electronic

Signature, the Status Register and the Common Flash Interface. Both Chip Enable and Output

Enable must be at VIL in order to perform a read operation. The Chip Enable input should be

used to enable the device. Output Enable should be used to gate data onto the output. The

data read depends on the previous command written to the memory (see Command Interface

section). See Figure 9, Figure 11 and Figure 12 Read AC Waveforms, and Table 22 and

Table 23 Read AC Characteristics, for details of when the output becomes valid.

3.2

Bus Write

Bus Write operations write Commands to the memory or latch Input Data to be programmed. A

bus write operation is initiated when Chip Enable and Write Enable are at VIL with Output

Enable at VIH. Commands, Input Data and Addresses are latched on the rising edge of Write

Enable or Chip Enable, whichever occurs first. The addresses can also be latched prior to the

write operation by toggling Latch Enable. In this case the Latch Enable should be tied to VIH

during the bus write operation. See Figure 15 and Figure 16, Write AC Waveforms, and

Table 24 and Table 25, Write AC Characteristics, for details of the timing requirements.

3.3

Address Latch

Address latch operations input valid addresses. Both Chip enable and Latch Enable must be at

VIL during address latch operations. The addresses are latched on the rising edge of Latch

Enable.

3.4

Output Disable

The outputs are high impedance when the Output Enable is at VIH.

3.5

Standby

Standby disables most of the internal circuitry allowing a substantial reduction of the current

consumption. The memory is in standby when Chip Enable and Reset are at VIH. The power

consumption is reduced to the standby level IDD3 and the outputs are set to high impedance,

independently from the Output Enable or Write Enable inputs. If Chip Enable switches to VIH

during a program or erase operation, the device enters Standby mode when finished.

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