34AA04T-ESLASHST datasheet(8/36 Pages) MICROCHIP

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34AA04

DS20005271B-page 8

 2014 Microchip Technology Inc.

5.0

BANK ADDRESSING

To support backwards-compatibility with DDR2/3

(JEDEC EE1002) SPD EEPROMs, the memory array

of the 34AA04 is divided into two separate 256-byte

banks. The Set Bank Address (SBA) commands are

used to set the bank address to either 0 or 1. The

Read Bank Address (RBA) command is used to

determine which bank is currently selected.

TABLE 5-1:

BANK ADDRESS RANGE

TABLE 5-2:

BANK ADDRESSING INSTRUCTION SET

5.1

Set Bank Address (SBA)

The Set Bank Address (SBA) commands are used to

select the array bank for future read and write

operations.

The master generates a Start condition followed by the

corresponding control byte for the chosen SBA

command (Table 5-2), with the R/W bit set to a logic

‘0’. Note that Chip Select bit A0 of the control byte

effectively determines which bank is selected. The

34AA04 will respond with an Acknowledge, and then

the master transmits two dummy bytes. The 34AA04

will not acknowledge either dummy byte. Finally, the

master generates a Stop condition to end the

operation (Figure 5-1).

Array Read and Write commands will operate in the

newly-selected bank until another SBA command is

executed, or the 34AA04 experiences a POR or BOR

event.

FIGURE 5-1:

SET BANK ADDRESS

Note 1:

The bank address is volatile and is reset

to Bank 0 upon power-up.

The comparison between the A0, A1, and

A2 pins and the corresponding Chip

Select bits is disabled for Bank Select

commands.

Note:

Sequential read operations cannot

cross a bank boundary and will roll over

back to the beginning of the selected

bank.

Bank

Logical Array Address

Bank 0

000h-0FFh

Bank 1

100h-1FFh

Function

Abbr

Control Byte

A0 Pin

Control Code

Chip Select Bits

R/W

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Set Bank Address to 0

SBA0

0110

1100

, 1, or VHV

Set Bank Address to 1

SBA1

1110

, 1, or VHV

Read Bank Address

RBA

1101

, 1, or VHV

Bus Activity

Master

SDA Line

Bus Activity

Control

Byte

Dummy

Byte

1 0

Dummy

Byte

Note 1:

Chip Select bit A0 specifies which bank to select.

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