Am79C965A
17
Table 5. Pin Connections to Power/Ground
If BRDY and RDYRTN are sampled active in the same
cycle, then RDYRTN takes precedence, causing the
next transfer cycle to begin with a T1 cycle.
BRDY functions as an output during PCnet-32
controller slave cycles and is always driven inactive
(HIGH).
BRDY is floated if the PCnet-32 controller is not being
accessed as the current slave device on the local bus.
D/C
Data/Control Select
During slave accesses to the PCnet-32 controller, the
D/C pin, along with M/IO and W/R, indicates the type of
cycle that is being performed. PCnet-32 controller will
only respond to local bus accesses in which D/C is
driven HIGH by the local bus master.
Input/Output
During PCnet-32 controller bus master accesses, the
D/C pin is an output and will always be driven HIGH.
D/C is floated if the PCnet-32 controller is not the
current master on the local bus.
DAT0
–
DAT31
Data Bus
Used to transfer data to and from the PCnet-32 control-
ler to system resources via the local bus. DAT31
–
DAT0
are driven by the PCnet-32 controller when performing
bus master writes and slave read operations. Data on
Input/Output
DAT31
–
DAT0 is latched by the PCnet-32 controller
when performing bus master reads and slave write
operations.
The PCnet-32 controller will always follow Am386DX
byte lane conventions. This means that for word and
byte accesses in which PCnet-32 controller drives the
data bus (i.e. master write operations and slave read
operations), the PCnet-32 controller will produce dupli-
cates of the active bytes on the unused half of the 32-
bit data bus. Table 6 illustrates the cases in which
duplicate bytes are created.
Table 6. Bye Duplication on Data Bus
*Note:
Byte duplication does not apply during an
LBS16 access, see Table 8.
Pin Name
Pin No
Supply
Strapping
Resistive
Connection
to Supply
Recommended
Resistor Size
LED2/SRDCLK
2
Required
Required
324
in series with LED, or 10 K
without LED
LBS16
25
Optional
Required
10 K
VLBEN
31
Required
Optional
NA
WBACK
54
Optional
Required
10 K
LREQI/TDO
100
Optional
Required
10 K
JTAGSEL
106
Required
Optional
NA
EEDO/LEDPRE3/SRD
152
Optional
Required
10 K
LB/VESA
153
Required
Optional
NA
EEDI/LNKST
154
Optional
Required
324
in series with LED, or 10 K
without LED
EESK/LED1SFBD
155
Required
Required
324
in series with LED, or 10 K
without LED
SLEEP
156
Optional
Required
10 K
All Other Pins
—
Optional
Required
10 K
BE3-BE0
DAT
[31:24]
Undef
Undef
Undef
A
Undef
Undef
D
Undef
D
D
DAT
[23:16]
Undef
Undef
A
Undef
Undef
C
C
C
C
C
DAT
[15:8]
Undef
A
Undef
Copy A
B
B
Copy D
B
B
B
DAT
[7:0]
A
Undef
Copy A
Undef
A
Undef
Copy C
A
Undef
A
1110
1101
1011
0111
1100
1001
0011*
1000
0001
0000