DESCRIPTION OF PIN FUNCTIONS
PQFP/TQFP
PIN NO.
7
NAME
nChip
Select
Output
nReceive
Packet
Discard
SYMBOL
nCSOUT
BUFFER
TYPE
O4
DESCRIPTION
Output. Chip Select provided for mapping of PHY
functions into LAN91C100FD decoded space.
Active on accesses to LAN91C100FD’s eight lower
addresses when the BANK SELECTED is 7.
Input. Used to discard the receive packet being
stored in memory. Assertion of the pin during a
packet reception results in the interruption of
packet reception into memory. The memory
allocated to the packet and the packet number in
use are freed. The input is driven asynchronously
and
is
synchronized
internally
by
the
LAN91C100FD. Pin assertion may take place at
any time during the receive DMA packet. The
assertion has no effect if there is no packet being
DMAed to memory or if asserted during the last
DMA write to memory. Works for both MII and
ENDEC. The typical use of nRXDISC is with the
LAN91C100FD in PRMS mode with an external
associative memory use for address filtering.
*Note: The pin must be asserted for a minimum
of 80ns.
Output. Active when the first dword of the address
is written (RCVDMA=1, RA10-RA4=0, RA3-
RA2=X).
8
nRXDISC
I with
pullup
37
RDMAH
O4
Buffer Types
O4
O12
O16
O24
OD16
I/O4
I/O24
I
IS
Iclk
Output buffer with 2mA source and 4mA sink
Output buffer with 6mA source and 12mA sink
Output buffer with 8mA source and 16mA sink
Output buffer with 12mA source and 24mA sink
Open drain buffer with 16mA sink
Bidirectional buffer with 2mA source and 4mA sink
Bidirectional buffer with 12mA source and 24mA sink
Input buffer with TTL levels
Input buffer with Schmitt Trigger Hysteresis
Clock input buffer
DC levels and conditions defined in the DC Electrical Characteristics section.
SMSC DS – LAN91C100FD REV. B
Page 9
Rev. 05/31/2000
SMSC [ SMSC CORPORATION ]
