AM79C987 AMD [Advanced Micro Devices], AM79C987 Datasheet - Page 13

• Manufacturer Part Number: AM79C987
• Description: Hardware Implemented Management Information Base (HIMIB) Device
• Manufacturer: AMD [Advanced Micro Devices]

Transmit Collisions
P[4:0] = 0, R[4:0] = 13
Byte 0
Byte 1
Byte 2
Byte 3
Transmit Collisions is a 4-byte read-only attribute that
counts the number of transmit collisions this repeater
has detected. The value of the Transmit Collisions at-
tribute is a 32-bit counter with a minimum rollover time of
15 hours.
The 4 bytes in this attribute are sequentially accessed
by reading the D Port, least significant byte first. Note
that once the C Port is programmed for access to this at-
tribute, reading the D Port causes the value of this regis-
ter to be copied to the internal holding register. The data
is then read from the holding register, without affecting
this attribute. This sequence is repeated when the last
byte is read and the D Port is accessed.
Configuration Register
P[4:0] = 0, R[4:0] = 16
This is a read/write register. The value read is the same
as that written. Only zeros should be written into unused
bits. All bits are cleared upon reset.
D Port Read/Write
I
E Interface Error Interrupt Enable. When this bit is set
S Source Address Match Interrupt Enable. When this
M MAC Interface Mode Enable. When this bit is set to 1,
MSB
I
Enable Interrupts. When this bit is set to 0, all inter-
rupts from this HIMIB device are masked (but not
cleared) and the INT output pin is forced to inactive
state (not driven).
to 1, the HIMIB device generates an interrupt if the
IMR+ interface is not functioning correctly.
bit is set, the HIMIB chip will generate an interrupt if
the Source Address of the received packet matches
that programmed into the Source Address Match
Register (in the Repeater Register Bank).
the HIMIB device is assumed to be interfaced to an
802.3/Ethernet MAC Controller. In this mode only
statistics for port 31 (AUI) are valid. The Expansion
Port interface statistics are reported for port 31
(AUI). The HIMIB chip must be kept in this mode until
an external reset occurs.
AMD
D Port Read
bit 31
MSB
bit 7
E
S
M
0
0
0
P R E L I M I N A R Y
bit 24
bit 0
LSB
0
LSB
Am79C987
When the HIMIB chip is interfaced to a MAC device,
such as AMD’s LANCE (Am7990) and MACE
(Am79C940) etc., the CRS pin from the MAC device
should be connected to the CRS pin of the HIMIB chip.
Also, the SO input pin of the HIMIB chip should be tied
HIGH. Note that in this mode, the HIMIB chip will report
an Interface Error in the Status Register since there is no
connection to the Management Port. Therefore, it is rec-
ommended that the Interface Error Interrupt is left dis-
abled. Certain attributes specific to the Repeater
Management Standard, such as bit rate error, AUI loop-
back error etc., will have no meaning.
Note: Once this bit is set by software, it should not be
cleared again as this may cause incorrect device
operation.
Version and Device ID Register
P[4:0] = 0, R[4:0] = 28
This is a read only register. The 8-bit read has the follow-
ing format:
D Port Read
V Version. These bits contain the HIMIB chip version
D Device ID. The HIMIB device detects the Repeater
Note: If the HIMIB chip detects an interface error upon
reset, then this field may not contain valid data.
IMR+ Management Port Set Register (S)
P[4:0] = 0, R[4:0] = 30
D Port Write
This is a write only register. This register is used for
sending a Set command to the IMR+ device. When a
byte is written to this register, the HIMIB chip will serial-
ize and transfer this byte to the IMR+ Management port.
MSB
MSB
V3
D7
code. Software may interrogate these bits to deter-
mine additional features that may be available with
future versions of the device. The original version is
0000.
version upon reset. This field is updated to report the
type of physical repeater attached to the HIMIB
device.
D
0
1
2–15
V2
D6
D5
V1
V0
D4
Device
IMR chip (Does not support all
attributes)
IMR+ chip
Reserved for future use
D3
D3
D2
D2
D1
D1
D0
D0
LSB
LSB
13