NEC Network Controller uPD98502 - Manual (Page 428)

CHAPTER 10 MICRO WIRE
428 Preliminary User’s Manual S15543EJ1V0UM
10.2 Operations
10.2.1 Data read at the power up load
After reset release, power up load processes starts.
In case of the value from EEPROM address 00H is:
1. A5A5H
System Controller sets the EEPROM data (address: 01H to 06H) in the internal registers (MACAR1,
MACAR2, MACAR3).
2. NOT A5A5H
System Controller sets the fix data “0000_0000H” in the internal registers (MACAR1, MACAR2, MACAR3).
Table 10-1. EEPROM Initial Data
EEPROM Address Data Stored Register
00H A5A5H -
01H MAC1 Address data[15:0] MACAR1[15:0]
02H MAC1 Address data[31:16] MACAR1[31:16]
03H MAC1 Address data[47:32] MACAR2[15:0]
04H MAC2 Address data[15:0] MACAR2[31:16]
05H MAC2 Address data[31:16] MACAR3[15:0]
06H MAC2 Address data[47:32] MACAR3[31:16]
10.2.2 Accessing to EEPROM
Access to EEPROM starts by writing to the ECCR (EEPROM Command Control Register).
Write command (3 bits) and address (6 bits) of EEPROM into lower 9 bits of ECCR.
There is a difference between write command and read command.
1. Write command
Write data into upper 16 bits of ECCR.
2. Read command
Data is loaded into lower 16bits of ERDR (EEPROM Read Data Register).
Table 10-2. EEPROM Command List
Command bits 8:6 bits 5:0 Operation
READ 110 A5:A0 Read data from EEPROM assigned by address A5:A0
EWEN 100 11xxxx Enable Erase/Write command.
This command must be executed before other operating.
ERASE 111 A5:A0 Erase data of EEPROM assigned by address A5:A0
WRITE 101 A5:A0 Write data to EEPROM assigned by address A5:A0
ERAL 100 10xxxx Erase all data of EEPROM.
WRAL 100 01xxxx Write all data to EEPROM.
EWDS 100 00xxxx Disable Erase/Write command.