LAN91C100 Datasheet, PDF (76/101 Pages) SMSC Corporation – FEAST™ Fast Ethernet Controller

EISA 32 BIT SLAVEEISA 32 BIT SLAVEEISA 32 BIT SLAVEEISA 32 BIT SLAVEEISA 32 BIT
SLAVEEISA 32 BIT SLAVEEISA 32 BIT SLAVEEISA 32 BIT SLAVEEISA 32 BIT SLAVE
On EISA, the LAN91C100 is accessed as a 32
bit I/O slave, along with a Slave DMA type "C"
data path option. As an I/O slave, the
LAN91C100 uses asynchronous accesses. In
creating nRD and nWR inputs, the timing
information is externally derived from nCMD
edges. Given that the access will be at least 1.5
to 2 clocks (more than 180ns at least) there is
no need to negate EXRDY, simplifying the EISA
interface
implementation. As a DMA
Slave, the LAN91C100 accepts burst transfers,
and is able to sustain the peak rate of one
doubleword every BCLK. Doubleword alignment
is assumed for DMA transfers. Up to 3 extra
bytes in the beginning and at the end of the
transfer should be moved by the CPU using I/O
accesses to the Data Register. The LAN91C100
will sample EXRDY and postpone DMA cycles if
the memory cycle solicits wait states.
EISA BUS
SIGNAL
LA2-15
M/nIO
AEN
Latched W-R
combined with
nCMD
Latched W-R
combined with
nCMD
nSTART
RESDRV
nBE0, nBE1,
nBE2, nBE3
IRQn
Table 5 - EISA 32 Bit Slave Signal Connections
LAN91C100 SIGNAL
NOTES
A2-A15
Address bus used for I/O space and register decoding,
latched by nADS (nSTART) trailing edge.
AEN
Qualifies valid I/O decoding - enabled access when low.
These signals are externally ORed. Internally the AEN pin
is latched by nADS rising edge and transparent while
nADS is low.
nRD
I/O Read strobe - Asynchronous read accesses. Address
is valid before its leading edge. Must not be active during
DMA bursts if DMA is supported.
nWR
I/O Write strobe - Asynchronous write access. Address is
valid before leading edge. Data latched on trailing edge.
Must not be active during DMA bursts if DMA is
supported.
nADS
Address strobe is connected to EISA nSTART.
RESET
nBE0, nBE1,
nBE2, nBE3
Byte enables. Latched on nADS rising edge.
INTR0-INTR3
Interrupts used as active high edge triggered.
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