AM79C961A_00 Datasheet, PDF (55/206 Pages) Advanced Micro Devices – PCnet™-ISA II Jumperless, Full Duplex Single-Chip Ethernet Controller for ISA

I/O Interrupt Configuration
Name
Interrupt request level
select 0
Interrupt request type
select 0
Register
Index
0x70
0x71
Definition
Read/write value indicating selected interrupt level. Bits[3:0] select which interrupt
level used for Interrupt 0. One selects IRQL 1, fifteen selects IRQL fifteen. IRQL 0 is
not a valid interrupt selection and represents no interrupt selection.
Read/write value indicating which type of interrupt is used for the Request Level
selected above.
Bit[1] : Level, 1 = high, 0 = low
Bit[0] : Type, 1 = level, 0 = edge
The PCnet-ISA II controller only supports Edge High and Level Low Interrupts.
DMA Channel Configuration
Name
Register
Index
Definition
DMA channel select 0
0x74
Read/write value indicating selected DMA channels. Bits[2:0] select which DMA
channel is in use for DMA 0. Zero selects DMA channel 0, seven selects DMA
channel 7. DMA channel 4, the cascade channel is used to indicate no DMA channel
is active.
DMA channel select 1
0x75 Read only with a value of 0x04.
DETAILED FUNCTIONS
EEPROM
Interface
The EEPROM supported by the PCnet-ISA II controller
is an industry standard 93C56 2-Kbit EEPROM device
which uses a 4-wire interface. This device directly inter-
faces to the PCnet-ISA II controller through a 4-wire
interface which uses 3 of the private data bus pins for
Data In, Data Out, and Serial Clock. The Chip Select
pin is a dedicated pin from the PCnet-ISA II controller.
Note: All data stored in the EEPROM is stored in bit-re-
versal format. Each word (16 bits) must be written into
the EEPROM with bit 15 swapped with bit 0, bit 14
swapped with bit 1, etc.
This is a 2-Kbit device organized as 128 x 16 bit words.
A map of the device as used in the PCnet-ISA II con-
troller is below. The information stored in the EEPROM
is as follows:
IEEE address 6 bytes
Reserved10 bytes
EISA ID4 bytes
ISACSRs14 bytes
Plug and Play Defaults19 bytes
8-Bit Checksum1 byte
External Shift Chain2 bytes
Plug and Play Config Info192 bytes
Important Note About The EEPROM
Byte Map
The user is cautioned that while the Am79C961A (PC-
net-ISA II) and its associated EEPROM are pin com-
patible to their predecessors the Am79C961
(PCnet-ISA⁺) and its associated EEPROM, the byte
map structure in each of the EEPROMs are different
from each other.
The EEPROM byte map structure used for the
Am79C961A PCnet-ISA II has the addition of “MISC
Config 2, ISACSR9" at word location 10Hex. The
EEPROM byte map structure used for the Am79C961
PCnet-ISA+ does not have this.
Therefore, should the user intend to replace the PC-
net-ISA⁺ with the PCnet-ISA II, care MUST be taken to
reprogram the EEPROM to reflect the new byte map
structure needed and used by the PCnet-ISA II. For
additional information, refer to the Am79C961 PC-
net-ISA⁺ data sheet (PID #18183) under the sections
entitled EEPROM and Serial EEPROM Byte Map.
Am79C961A
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