always true, regardless of the setting of the SSIZE32
bit.
Initialization Block
Note: When SSIZE32 (BCR20, bit 8) is set to 0, the
software structures are defined to be 16 bits wide. The
base address of the initialization block must be aligned
to a DWord boundary, i.e., CSR1, bit 1 and 0 must be
cleared to 0. When SSIZE32 is set to 0, the initialization
block looks like Table 78.
When SSIZE32 (BCR20, bit 8) is set to 1, the software
structures are defined to be 32 bits wide. The base ad-
dress of the initialization block must be aligned to a
DWord boundary, i.e., CSR1, bits 1 and 0 must be
cleared to 0. When SSIZE32 is set to 1, the initialization
block looks like Table 79.
Note: The Am79C978 controller performs DWord ac-
cesses to read the initialization block. This statement is
Table 78. Initialization Block (SSIZE32 = 0)
Bits 15-13 Bit 12 Bits 11-8
Address
IADR+00h
IADR+02h
IADR+04h
IADR+06h
IADR+08h
IADR+0Ah
IADR+0Ch
IADR+0Eh
IADR+10h
IADR+12h
IADR+14h
IADR+16h
Bits 7-4
Bits 3-0
MODE 15-00
PADR 15-00
PADR 31-16
PADR 47-32
LADRF 15-00
LADRF 31-16
LADRF 47-32
LADRF 63-48
RDRA 15-00
RES
RLEN
TLEN
0
0
TDRA 23-16
TDRA 23-16
TDRA 15-00
RES
Table 79. Initialization Block (SSIZE32 = 1)
Bits
31-28
TLEN
Bits
27-24
RES
Bits
Bits
19-16
RES
Bits
Bits
11-8
Bits
7-4
Bits
3-0
Address
23-20
RLEN
15-12
IADR+00h
IADR+04h
IADR+08h
IADR+0Ch
IADR+10h
IADR+14h
IADR+18h
MODE
PADR 31-00
RES
PADR 47-32
LADRF 31-00
LADRF 63-32
RDRA 31-00
TDRA 31-00
RLEN and TLEN
listed in Table 80 is desired, CSR76 and CSR78 can be
written after initialization is complete.
When SSIZE32 (BCR20, bit 8) is set to 0, the software
structures are defined to be 16 bits wide, and the RLEN
and TLEN fields in the initialization block are each three
bits wide. The values in these fields determine the num-
ber of transmit and receive Descriptor Ring Entries
(DRE) which are used in the descriptor rings. Their
meaning is shown in Table 80. If a value otherthan those
When SSIZE32 (BCR20, bit 8) is set to 1, the software
structures are defined to be 32 bits wide, and the RLEN
and TLEN fields in the initialization block are each 4 bits
wide. The values in these fields determine the number
of transmit and receive Descriptor Ring Entries (DRE)
which are used in the descriptor rings. Their meaning
is shown in Table 81.
198
Am79C978
AMD [ AMD ]
