IA21140AF
Preliminary Data Sheet
PCI FAST ETHERNET LAN CONTROLLER
I/O Description
The following section provides a functional description of the I/O pins on the IA21140AF.
NAME
Type
Description
Vdd
P
3.3 volt input supply voltage.
Vdd_clamp
P
5.0 volt reference for 5.0 volt signaling environments and 3.3 volt reference
for 3.3 volt signaling environments.
Vss
P
Ground Pin
ad[31:0]
I/O
The PCI address and data lines are multiplexed on the same PCI pins. During
the first clock cycle of a transaction, the 32 bits contain an address and during
subsequent clock cycles, they contain data. Both read and write bursts are
supported in master operation only. Big or Little Indian byte ordering can be
used.
br_a[1:0]
O
Address line bit 0 also carries in two consecutive address cycles (bits 16 and
17) in a 256KB configuration. Bit 1 also latches the boot ROM address and
control lines via two external latches.
br_ad[7:0]
I/O
In the first of two consecutive address cycles, these multiplexed lines contain
the boot ROM address bits [7:2], oe_n, and we_n. The second cycle contains
boot ROM address bits [15:8]. Bits 7 through 0 contain data during the data
cycle. These lines are used to carry data to and from the external register.
br_ce_n
O
Enable pin for the Boot ROM or an external register. Pin has an internal 5 k O
pull-up resistor.
c_be_n[3:0]
I/O
Bus command and byte enable are multiplexed on the same PCI pins. These
bits provide the bus command during the address phase of the transaction.
They provide the byte enable during the data phase. Byte enable determines
which byte lines carry valid data. Bit 0 coincides with byte 0. Bit 1 coincides
with byte 1, etc.
devsel_n
frame_n
I/O
I/O
Indicates that the driving device has decoded its address as the target of the
current access. As an input, determines whether a device on the bus has
been selected.
The IA21140AF bus master asserts this signal to indicate the beginning and
duration of a bus transaction access. Data transfer continues while this signal
is asserted. Deasserting this signal indicates the transaction is in the final
phase.
gep[7:0]
I/O
These pins can be configured by software to perform either input or output
functions for system specific applications.
gnt_n
Idsel
I
I
Indicates to the IA21140AF that access to the bus has been granted.
Used as a chip select by the host to indicate configuration read and write
cycles.
int_n
O/D
When one of the appropriate bits in CSR5 gets set, interrupt request gets
asserted if the corresponding mask bit in CSR7 is not set. If more than one
interrupt bit in CSR5 is set and all input bits are not cleared, interrupt request
gets deasserted for one clock cycle. Interrupt request gets deasserted by
writing a “1” into the appropriate CSR5 bit. This pin must be pulled up by an
external resistor.
Copyright 2001
innovASIC
ENG210010110-00
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