Instruction Manual

DS271F5 47
CS8900A
Crystal LAN™ Ethernet Controller
CIRRUS LOGIC PRODUCT DATASHEET
The lower three bytes (0030h, 0031h, and 0032h) of the Boot PROM Base Address register are used for the 20-bit
Boot PROM base address. The upper three nibbles are reserved. See Section 3.6 on page 26.
After reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM
is found, then the register's initial value may be set by the EEPROM. See Section 3.3 on page 19.
Reset value is: XXXX XXXX XXXX 0000 0000 0000 0000 0000
4.3.10 Boot PROM Address Mask
(Read/Write, Address: PacketPage base + 0034h)
The Boot PROM address mask register indicates the size of the attached Boot PROM and is limited to 4K bit incre-
ments. The lower 12 bits of the Address Mask are ignored, and should be 000h. The next lowest-order bits describe
the size of the PROM. The upper three nibbles are reserved.
For example:
See Section 3.6 on page 26.
After reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM
is found, then the register's initial value may be set by the EEPROM. See Section 3.3 on page 19.
Reset value is: XXXX XXXX XXXX 0000 0000 0000 0000 0000
4.3.11 EEPROM Command
(Read/Write, Address: PacketPage base + 0040h)
This register is used to control the reading, writing and erasing of the EEPROM. See Section 3.5.
ADD7-ADD0 Address of the EEPROM word being accessed.
OB1,OB0 Indicates the Opcode of the command being executed. See Table 8.
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.
Reserved Reserved and must be written as 0.
Address 0037h Address 0036h Address 0035h Address 0034h
Reserved
The most significant nibble of
Boot PROM mask address.
The high-order nibble is
reserved.
Contains portion of Boot PROM
mask address. The lower-order
nibble must be written as 0h.
The least significant byte of
the Boot PROM mask
address. Must be written as
00h.
Size of Boot PROM Register value
4k bits XXXX XXXX XXXX 1111 1111 0000 0000 0000
8k bits XXXX XXXX XXXX 1111 1110 0000 0000 0000
16k bits XXXX XXXX XXXX 1111 1100 0000 0000 0000
76543210
ADD7 to ADD0
FEDCBA9 8
Reserved ELSEL OB1 OB0