M7040N datasheet(134/159 Pages) STMICROELECTRONICS

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M7040N

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SRAM READ with a Table of Up to 31 Devices

The following explains the SRAM READ operation

accomplished through a table of up to 31 devices,

using the following parameters: TLSZ = 10. The di-

agram of such a table is shown in Figure 100,

page 135.

The following assumes that SRAM access is being

accomplished through M7040N Device 0 and that

Device 0 is the selected device. Figure 101, page

136 and Figure 102, page 137 show the timing di-

agrams for Device 0 and Device 30, respectively.

– Cycle 1A: The host ASIC applies the READ In-

struction to CMD[1:0] using CMDV = 1. The DQ

Bus supplies the address, with DQ[20:19] set to

'10,' to select the SRAM address. The host

ASIC selects the device for which the ID[4:0]

matches the DQ[25:21] lines. During this cycle,

the host ASIC also supplies SADR[23:21] on

CMD[8:6].

– Cycle 1B: The host ASIC continues to apply the

READ Instruction to CMD[1:0] using CMDV = 1.

The DQ Bus supplies the address, with

DQ[20:19] set to '10,' to select the SRAM ad-

dress.

– Cycle 2: The host ASIC floats DQ[71:0] to a 3-

state condition.

– Cycle 3: The host ASIC keeps DQ[71:0] in a 3-

state condition.

– Cycle 4: Theselected devicestarts todrive

DQ[71:0].

– Cycles 5 to 6: The selected device continues to

drive DQ[71:0].

– Cycle 7: The selected device continues to drive

DQ[71:0] and drives an SRAM READ cycle.

– Cycle 8: The selected device drives ACK from

Zto low.

– Cycle 9: The selected device drives ACK to

high.

– Cycle 10: The selected device drives ACK from

high to low.

At the end of Cycle 10, the selected device floats

ACK in a 3-state condition.

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