M50FW040 datasheet(11/41 Pages) STMICROELECTRONICS

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M50FW040

BUS OPERATIONS

The two interfaces have similar bus operations but

the signals and timings are completely different.

The Firmware Hub (FWH) Interface is the usual in-

terface and all of the functionality of the part is

available through this interface. Only a subset of

functions are available through the Address/Ad-

dress Multiplexed (A/A Mux) Interface.

Follow the section Firmware Hub (FWH) Bus Op-

erations below and the section Address/Address

Multiplexed (A/A Mux) Bus Operations below for a

description of the bus operations on each inter-

face.

Firmware Hub (FWH) Bus Operations

The Firmware Hub (FWH) Interface consists of

four data signals (FWH0-FWH3), one control line

(FWH4) and a clock (CLK). In 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 de-

signed to be compatible with PCI electrical specifi-

cations. 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 Firmware Hub Registers. A valid Bus

Read operation starts when Input Communication

Frame, FWH4, is Low, VIL, as Clock rises and the

correct Start cycle is on FWH0-FWH3. On the fol-

lowing clock cycles the Host will send the Memory

ID Select, Address and other control bits on

FWH0-FWH3. The memory responds by output-

ting Sync data until the wait-states have elapsed

followed by Data0-Data3 and Data4-Data7.

Refer to Table 4., FWH Bus Read Field Defini-

tions, and Figure 7., FWH Bus Read Waveforms,

for a description of the Field definitions for each

clock cycle of the transfer. See Table 20., FWH In-

terface AC Signal Timing Characteristics, and Fig-

ure

12., FWH

Interface

Signal

Timing

Waveforms, for details on the timings of the sig-

nals.

Bus Write. Bus Write operations write to the

Command Interface or Firmware Hub Registers. A

valid Bus Write operation starts when Input Com-

munication Frame, FWH4, is Low, VIL, as Clock

rises and the correct Start cycle is on FWH0-

FWH3. On the following Clock cycles the Host will

send the Memory ID Select, Address, other control

bits, Data0-Data3 and Data4-Data7 on FWH0-

FWH3. The memory outputs Sync data until the

wait-states have elapsed.

Refer to Table 5., FWH Bus Write Field Defini-

tions, and Figure 8., FWH Bus Write Waveforms,

for a description of the Field definitions for each

clock cycle of the transfer. See Table 20., FWH In-

terface AC Signal Timing Characteristics, and Fig-

ure

12., FWH

Interface

Signal

Timing

Waveforms, for details on the timings of the sig-

nals.

Bus Abort. The Bus Abort operation can be used

to immediately abort the current bus operation. A

Bus Abort occurs when FWH4 is driven Low, VIL,

during the bus operation; the memory will tri-state

the Input/Output Communication pins, FWH0-

FWH3.

Note that, during a Bus Write operation, the Com-

mand Interface starts executing the command as

soon as the data is fully received; a Bus Abort dur-

ing the final TAR cycles is not guaranteed to abort

the command; the bus, however, will be released

immediately.

Standby. When FWH4 is High, VIH, the memory

is put into Standby mode where FWH0-FWH3 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 10. If RP or

INIT goes Low, VIL, during a Program or Erase op-

eration, 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.

Address/Address Multiplexed (A/A Mux) Bus

Operations

The Address/Address Multiplexed (A/A Mux) Inter-

face has a more traditional style interface. The sig-

nals consist of a multiplexed address signals (A0-

A10), data signals, (DQ0-DQ7) and three control

signals (RC, G, W). An additional signal, RP, can

be used to reset the memory.

The Address/Address Multiplexed (A/A Mux) Inter-

face is included for use by Flash Programming

equipment for faster factory programming. Only a

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