M50LPW002K datasheet(9/39 Pages) STMICROELECTRONICS

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M50LPW002

BUS OPERATIONS

The two interfaces have similar bus operations but

the signals and timings are completely different.

The Low Pin Count (LPC) Interface is the usual

interface and all of the functionality of the part is

available through this interface. Only a subset of

functions are available through the Address/

Address Multiplexed (A/A Mux) Interface.

Follow the section Low Pin Count (LPC) Bus

Operations below and the section Address/

Address Multiplexed (A/A Mux) Interface Bus

Operations below for a description of the bus

operations on each interface.

Low Pin Count (LPC) Bus Operations

The Low Pin Count (LPC) Interface consists of

four data signals (LAD0-LAD3), one control line

(LFRAME)

and

clock

(CLK).

addition

protection against accidental or malicious data

corruption can be achieved using two further

signals (TBL and WP). Finally two reset signals

(RP and INIT) are available to put the memory into

a known state.

The data signals, control signal and clock are

designed to be compatible with PCI electrical

specifications. The interface operates with clock

speeds up to 33MHz.

The following operations can be performed using

the appropriate bus cycles: Bus Read, Bus Write,

Standby, Reset and Block Protection.

Bus Read. Bus Read operations read from the

memory cells, specific registers in the Command

Interface or Low Pin Count Registers. A valid Bus

Read operation starts when Input Communication

Frame, LFRAME, is Low, VIL, as Clock rises and

the correct Start cycle is on LAD0-LAD3. On the

following clock cycles the Host will send the Cycle

Type + Dir, Address and other control bits on

LAD0-LAD3. The memory responds by outputting

Sync data until the wait-states have elapsed

followed by Data0-Data3 and Data4-Data7.

Refer to Table 5, Bus Read Field Definitions (LPC

Interface), and Figure 5, Bus Read Waveforms

(LPC Interface), for a description of the Field defi-

nitions for each clock cycle of the transfer. See Ta-

ble 22, AC Signal Timing Characteristics (LPC

Interface), and Figure 10, AC Signal Timing Wave-

forms (LPC Interface), for details on the timings of

the signals.

Bus Write. Bus Write operations write to the

Command Interface or Low Pin Count Registers. A

valid Bus Write operation starts when Input

Communication Frame, LFRAME, is Low, VIL, as

Clock rises and the correct Start cycle is on LAD0-

LAD3. On the following Clock cycles the Host will

send the Cycle Type + Dir, Address, other control

bits, Data0-Data3 and Data4-Data7 on LAD0-

LAD3. The memory outputs Sync data until the

wait-states have elapsed.

Refer to Table 6, Bus Write Field Definitions (LPC

Interface), and Figure 6, Bus Write Waveforms

(LPC Interface), for a description of the Field

definitions for each clock cycle of the transfer. See

Table 22, AC Signal Timing Characteristics (LPC

Interface), and Figure 10, AC Signal Timing

Waveforms (LPC Interface), for details on the

timings of the signals.

Bus Abort. The Bus Abort operation can be used

to immediately abort the current bus operation. A

Bus Abort occurs when LFRAME is driven Low,

VIL, during the bus operation; the memory will tri-

state

the

Input/Output

Communication

pins,

LAD0-LAD3.

Note that, during a Bus Write operation, the

Command

Interface

starts

executing

the

command as soon as the data is fully received; a

Bus Abort during the final TAR cycles is not

guaranteed to abort the command; the bus,

however, will be released immediately.

Standby. When LFRAME is High, VIH, the

memory is put into Standby mode where LAD0-

LAD3 are put into a high-impedance state and the

Supply Current is reduced to the Standby level,

ICC1.

Reset. During Reset mode all internal circuits are

switched off, the memory is deselected and the

outputs are put in high-impedance. The memory is

in Reset mode when Interface Reset, RP, or CPU

Reset, INIT, is Low, VIL. RP or INIT must be held

Low, VIL, for tPLPH. The memory resets to Read

mode upon return from Reset mode and the Lock

Registers return to their default states regardless

of their state before Reset, see Table 13. If RP or

INIT goes Low, VIL, during a Program or Erase

operation, the operation is aborted and the

memory cells affected no longer contain valid

data; the memory can take up to tPLRH to abort a

Program or Erase operation.

Block Protection. Block

Protection

can

forced using the signals Top Block Lock, TBL, and

Write Protect, WP, regardless of the state of the

Lock Registers.

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