CS89712 datasheet(45/170 Pages) CIRRUS

45 / 170 page

CS89712

DS502PP2

Section 2.32, “Basic Receive Operation” and Sec-

tion 2.32.7, “Receive Ethernet Port Locations”

provide a detailed description of packet reception.

2.24 Programming the EEPROM

After initialization, software can access the EE-

PROM through the Ethernet port by writing one of

seven commands to the EEPROM Command regis-

ter. Figure 12 shows the format of the EEPROM

Command register.

2.24.1

EEPROM Commands

The seven commands used to access the EEPROM

are: Read, Write, Erase, Erase/Write Enable,

Erase/Write Disable, Erase-All, and Write-All.

They are described in Table 26.

2.24.2

EEPROM Command Execution

During the execution of a command, the two Op-

code bits, followed by the six bits of address (for a

’C46 or ’CS46) or eight bits of address (for a ’C56,

’CS56, ’C66 or ’CS66), are shifted out of the Ether-

net port, into the EEPROM. If the command is a

Write, the data in the EEPROM Data register

(Ethernet Port offset address 0042h) follows. If the

command is a Read, the data in the specified EE-

PROM location is written into the EEPROM Data

no data is transferred to or from the EEPROM Data

BUSY bit (Register 16, SelfST, bit 8) must clear.

After each command has been issued, software

must wait again for SIBUSY to clear.

2.24.3

Enabling Access to the EEPROM

The Erase/Write Enable command provides protec-

tion from accidental writes to the EEPROM. The

software must write an Erase/Write Enable com-

mand before it attempts to write to or erase any EE-

PROM memory location. Once the software has

finished altering the contents of the EEPROM, it

must write an Erase/Write Disable command to

prevent unwanted modification of the EEPROM.

ELSEL OP1 OP0

AD5 AD4

AD7 AD6

AD1 AD0

AD3 AD2

AD5 - AD0 used with

’C46 and ’CS46

AD7 - AD0 used with ’C56,

’CS56, ’C66 and ’CS66

Figure 12. EEPROM Command Register Format

Bit

Name

Description

[F:B]

Reserved

[A]

ELSEL

External Logic Select: When clear, the EECS pin is used to select the EEPROM.

When set, the ELCS pin is used to select the external LA decode circuit.

[9:8]

OP1, OP0

Opcode: Indicates what command is being executed (see next section).

[7:0]

AD7 to AD0

EEPROM Address: Address of EEPROM word being accessed.

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