am79c974 Advanced Micro Devices, am79c974 Datasheet - Page 23

• Manufacturer Part Number: am79c974
• Description: Pcnettm-scsi Combination Ethernet And Scsi Controller For Pci Systems
• Manufacturer: Advanced Micro Devices

at the PCnet-SCSI controller Microwire interface. At the
trailing edge of the RST signal, EESK is sampled to de-
termine the value of the EEDET bit in BCR19. A sam-
pled HIGH value means that an EEPROM is present,
and EEDET will be set to ONE. A sampled LOW value
means that an EEPROM is not present, and EEDET will
be set to ZERO. See the EEPROM Auto-detection sec-
tion for more details.
EESK is shared with the LED1 function. If no LED circuit
is to be attached to this pin, then a pull up or pull down
resistor must be attached instead, in order to resolve the
EEDET setting.
EEDO
EEPROM Data Out
Input
The EEDO signal is used to access the external ISO
8802-3 (IEEE/ANSI 802.3) address PROM. This pin is
designed to directly interface to a serial EEPROM that
uses the Microwire interface protocol. EEDO is con-
nected to the Microwire EEPROM’s Data Output pin. It
is controlled by the EEPROM during reads. It may be
read by the host system by reading BCR19 bit 0.
EEDO is shared with the LED3 function.
EECS
EEPROM Chip Select
Output
The function of the EECS signal is to indicate to the
Microwire EEPROM device that it is being accessed.
The EECS signal is active high. It is controlled by either
the PCnet-SCSI controller during command portions of
a read of the entire EEPROM, or indirectly by the host
system by writing to BCR19 bit 2.
EEDI
EEPROM Data In
Output
The EEDI signal is used to access the external ISO
8802-3 (IEEE/ANSI 802.3) address PROM. EEDI func-
tions as an output. This pin is designed to directly inter-
face to a serial EEPROM that uses the Microwire
interface protocol. EEDI is connected to the Microwire
EEPROM’s Data Input pin. It is controlled by either the
PCnet-SCSI controller during command portions of a
read of the entire EEPROM, or indirectly by the host sys-
tem by writing to BCR19 bit 0.
EEDI is shared with the LNKST function.
P R E L I M I N A R Y
Am79C974
Attachment Unit Interface
CI
Collision In
Input
A differential input pair signaling the PCnet-SCSI con-
troller that a collision has been detected on the network
media, indicated by the CI inputs being driven with a
10 MHz pattern of sufficient amplitude and pulse width
to meet ISO 8802-3 (IEEE/ANSI 802.3) standards. Op-
erates at pseudo ECL levels.
DI
Data In
Input
A differential input pair to the PCnet-SCSI controller car-
rying Manchester encoded data from the network. Oper-
ates at pseudo ECL levels.
DO
Data Out
Output
A differential output pair from the PCnet-SCSI controller
for transmitting Manchester encoded data to the net-
work. Operates at pseudo ECL levels.
Twisted-Pair Interface
RXD
10BASE-T Receive Data
Input
10BASE-T port differential receivers.
TXD
10BASE-T Transmit Data
Output
10BASE-T port differential drivers.
TXP
10BASE-T Pre-Distortion Control
Output
These outputs provide transmit pre-distortion control in
conjunction with the 10BASE-T port differential drivers.
AMD
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