STTS2004 datasheet(9/58 Pages) STMICROELECTRONICS

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STTS2004

Serial communications

The SPD memory may be accessed using a DTI of (1010), and to perform the SWPn,

RSPn, or CWP operations, a DTI of (0110) is required.

The DTI codes are:



'0011' for the TS, and



'1010' for addressing the EEPROM memory array, and



‘0110’ to access the software write protection settings of the EEPROM

2.1.1

I2C slave sub-address decoding

The 7-bit address for STTS2004 device consists of the 4-bit DTI code and the 3-bit device

select code from the state of the 3 address pins (device select code) which are combined as

shown in Table 2.

The 8th bit is the Read/Write bit (R/W). This bit is set to 1 for Read and 0 for Write

operations.

If a match occurs on the device select code, the corresponding device gives an

acknowledgment on serial data (SDA) during the 9th bit time.

The physical address for the TS is different than that used by the EEPROM. The TS

physical address is binary 0 0 1 1 A2 A1 A0 RW, where A2, A1, and A0 are the three slave

sub- address pins, and the LSB "RW" is the READ/WRITE flag.

The EEPROM physical address is binary 1 0 1 0 A2 A1 A0 RW for the memory array and is

0 1 1 0 A2 A1 A0 RW for permanently set write protection mode.

Thus up to eight STTS2004 devices can be connected on a single I2C bus. Each device is

given a unique 3-bit Logical Serial Address code. The LSA is a decoding of information on

the address pins A0, A1, and A2 as described in Table 1. When the Device Select Code is

received, the device only responds if the Select Address is the same as the Logical Serial

Address.

Table 1. Logical serial address according to A2, A1, A0

Write protection commands SWPn, CWP, and RPSn, and the SPD page address

commands SPAn and RPA, do not use the select address A(n) or logical serial address

(LSA), therefore all devices on the bus will act on these commands simultaneously. Since it

is impossible to determine which device is responding to RPSn or RPA commands, for

example, these functions are primarily used for external device programmers rather than in-

system applications.

Logical serial address

(LSA)

Device select code

000

0 (VSS)

001

0 (VSS)

1 (VDD)

010

0 (VSS)

1 (VDD)

0 (VSS)

011

0 (VSS)

1 (VDD)

100

1 (VDD)

0 (VSS)

101

1 (VDD)

0 (VSS)

1 (VDD)

110

1 (VDD)

0 (VSS)

111

1 (VDD)

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