P R E L I M I N A R Y
AMD
161
Am79C965
value of ZERO. Any attempt to
change this value by writing to
the BWRITE bit location will have
no effect.
4-3 TSTSHDW
Test Shadow bits. These bits are
used to place the PCnet-32 con-
troller into GPSI mode. BCR18[3]
must be set to ZERO. The oper-
ating modes possible are indi-
cated in Table 47.
See Table 48 for pin reconfigura-
tion in GPSI mode.
Table 47. GPSI Mode Selection
TSTSHDW
Value
PVALID
GPSIEN
Operating
(BCR18[4:3])
(BCR19[15])
(CSR124[4])
Mode
00
X
0
Normal
Operating
Mode
10
1
X
GPSI Mode
01
1
0
Reserved
11
1
X
Reserved
XX
0
Normal
Operating
Mode
XX
0
1
GPSI Mode
Note that when the GPSI mode is
invoked, only the lower 24 bits of
the address bus are available.
IOAW24 (BCR21[8]) must be
set to allow slave operations.
During master accesses in GPSI
mode, the PCnet-32 controller
will not drive the upper 8 bits
of the address bus with address
information.
These bits are not writeable, re-
gardless of the setting of the
ENTST bit in CSR4. Values may
only be programmed to these bits
through the EEPROM read op-
eration.
BCR18[4:3] are set to 0 by
H_RESET and are unaffected by
S_RESET or STOP.
2-0
LINBC[2:0]
Linear Burst Count. The 3-bit
value in this register sets the up-
per limit for the number of trans-
fer cycles in a Linear Burst. This
limit determines how often the
PCnet-32 controller will assert
the
ADS signal during linear
burst transfers. Each time that
the interpreted value of LINBC
transfers
is
reached,
the
PCnet-32 controller will assert
the
ADS signal with a new valid
address.
The
LINBC
value
should contain only one active
bit. LINBC values with more than
one active bit may produce pre-
dictable results, but such values
will not be compatible with future
AMD network controllers. The
LINBC entry is shifted by two bits
before
being
used
by
the
PCnet-32 controller. For exam-
ple, the value LINBC[2:0] = 010 is
understood by the PCnet-32 con-
troller to mean 01000 = 8. There-
fore, the value LINBC[2:0] = 010
will cause the PCnet-32 control-
ler to issue a new
ADS every
Table 48. GPSI Pin Configurations
GPSI
PCnet-32/
PCnet-32
I/O
LANCE
ILACC
PCnet-ISA
Pin
Normal
GPSI Function
Type
GPSI Pin
Number
Pin Function
Transmit Data
O
TX
TXD
TXDAT
132
A31
Transmit Enable
O
TENA
RTS
TXEN
133
A30
Transmit Clock
I
TCLK
TXC
STDCLK
134
A29
Collision
I
CLSN
CDT
CLSN
137
A28
Receive Carrier Sense
I
RENA
CRS
RXCRS
138
A27
Receive Clock
I
RCLK
RXC
SRDCLK
140
A26
Receive Data
I
RX
RXD
RXDAT
141
A25