MU9C8148
PIN DESCRIPTIONS (CONT’D)
RXC
(Receive Clock, Input, TTL)
D15–D0
(Data, Common I/O, TTL)
The rising edge of RXC clocks the RXD data received by the
TMS38053/4 from the Token Ring. The RXC clock is also used
to generate the control signals to the LANCAM, and controls
the internal operation of the MU9C8148.
The Data pins transfer data between the Host Processor and
the internal registers of the MU9C8148. The data pins are
registered on the falling edge of /HBRDY in the Write mode,
and are valid on the falling edge of /HBRDY in the Read mode,
as shown in the Timing diagrams.
/RDY
(Ring Interface Ready, Input, TTL)
/RS, /LDS
(Read Strobe/Lower Data Strobe,
Input, TTL)
The /RDY pin is taken LOW by the TMS38053/4 to indicate the
presence of received data. /RDY must be HIGH if the RXD data
is not valid.
In the Intel mode, this pin is /RS and is taken LOW to begin a
read cycle to the Host Processor interface. Data on D(15-0) is
valid when /HBRDY goes LOW. In the Motorola mode, this pin
is /LDS for Host processor read and write cycles. The falling
edge of /LDS or /UDS begins the cycle; data is strobed when
/HBRDY goes LOW for a Write cycle, and is valid on D(15-0)
when /HBRDY goes LOW for a Read cycle.
MAC Interface:
XMATCH
(Match, Output, Three-state TTL)
XMATCH goes HIGH in combination with XFAIL going LOW to
indicate that the frame currently being received should be
copied. If XFAIL is HIGH, XMATCH is forced LOW.
/WS, /UDS
(Write Strobe/Upper Data Strobe,
Input, TTL)
XFAIL, /FLUSH
(FAIL/FLUSH, Output,
Three-state TTL)
In the Intel mode, this pin is /WS, and is taken LOW to begin a
write cycle from the Host Processor interface. Data on D(15-0)
is strobed into the MU9C8148 when /HBRDY goes LOW. In the
Motorola mode, this pin is /UDS for Host processor read and
write cycles. The falling edge of /LDS or /UDS begins the Write
cycle; data is strobed when /HBRDY goes LOW for a Write
cycle, and is valid on D(15-0) when /HBRDY goes LOW for a
Read cycle.
The function of this pin is defined by the Control register. If the
MU9C8148 is connected to a TMS380CX6, this pin is defined
as XFAIL, which goes HIGH when XMATCH goes LOW, to tell
the TMS380CX6 to discard the frame and flush the receive
buffer.
Host Processor Interface:
/HBRDY
(Ready, Output, Three-state TTL)
ALE, SRNW (Address Latch Enable/System Read
Not Write, Input, TTL)
/HBRDY goes LOW to indicate to the Host processor that a
data transfer is completed for a Write cycle or that data is valid
for a Read cycle. After the Host processor takes /RS, /WS, or
/LDS and /UDS HIGH, the MU9C8148 takes /HBRDY HIGH.
/HBRDY becomes three-state one RXC period after it goes
HIGH, or when /CS goes HIGH.
This pin is ALE when the MU9C8148 is used in the Intel mode.
The falling edge of ALE latches the address on the address
lines. If the MU9C8148 is in the Motorola mode, this pin
becomes SRNW, and is HIGH for a Host Processor Read cycle
and LOW for a Write cycle.
/HBEN
(Data Buffer Enable, Output, TTL)
/CS
(Chip Select, Input, TTL)
/HBEN goes LOW to enable external bi-directional buffers, if
are needed on the D15–D0 lines. /HBEN goes HIGH to disable
the external buffers.
/CS going LOW enables the Host Processor interface of the
MU9C8148 for a Host Processor read or write. When /CS is
HIGH, /HBRDY goes three-state and the Host Processor
interface is disabled.
/HBDIR
(Data Buffer Direction, Output, TTL)
/HBDIR controls the direction of data flow in external
bi-directional buffers. /HBDIR goes LOW to enable data flowing
to the MU9C8148 and HIGH to enable data coming from the
MU9C8148 registers.
A4–A0
(Address, Input, TTL)
The Address pins select the internal register for Host processor
reads and writes. In the Intel mode, the Address pins are
latched by the falling edge of ALE. In the Motorola mode, the
Address pins must remain stable until the rising edge of /LD
and /UDS, as shown in the Timing diagrams.
/INT
(Interrupt, Output, Open Drain)
This pin goes LOW to notify the Host processor that the
MU9C8148 is running an Instruction Buffer routine, therefore
accessing the LANCAM. /INT will remain LOW as long the
routine is running.
Rev. 5.5 Draft web
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MUSIC [ MUSIC SEMICONDUCTORS ]
