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TNETX3270
ThunderSWITCH 24/3 ETHERNET SWITCH
WITH 24 10-MBIT/S PORTS AND 3 10-/100-MBIT/S PORTS
SPWS043B – NOVEMBER 1997 – REVISED APRIL 1999
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions (Continued)
host DIO interface
TERMINAL
I/O
INTERNAL
DESCRIPTION
NAME NO.
I/O
RESISTOR
DESCRIPTION
SAD1
SAD0
143
142
I Pullup DIO address bus. SAD1 and SAD0 select the internal host registers, when SDMA is high.
SCS
138 I Pullup DIO chip select. When low, SCS indicates a DIO port access is valid.
SDMA
123 I Pullup
DIO DMA select. When low, SDMA modifies the behavior of the DIO interface to allow it to operate
with an external DMA controller. The SAD0 and SAD1 terminals are not used to select the internal
host register for the access. Instead, the DIO address to access is provided by the DMA address
register, and one of two host register addresses is selected according to DMAinc in the Syscontrol
register.
– If DMAinc = 1, accesses are the DIOdatainc register and DMAaddress increments after each
access.
– If DMAinc = 0, accesses are the DIOdata register, and DMAaddress does not increment after
each address.
SDATA7
SDATA6
SDATA5
SDATA4
SDATA3
SDATA2
SDATA1
SDATA0
136
135
133
131
130
129
127
126
I/O Pullup
DIO data interface bus (byte-wide bidirectional DIO port). SDATA7 is the most significant bit and
SDATA0 is the least significant bit.
SINT
140 O None
DIO interrupt line (interrupt to the attached microprocessor). The interrupt originating event is
stored in the Int register.
SRDY
139 O Pullup
DIO ready signal
– When low during reads, SRDY
indicates to the host when data is valid to be read.
– When low during writes, SRDY
indicates when data has been received after SCS is taken
high. SRDY
is driven high for one clock cycle before placing the output in high impedance.
SRNW
125 I Pullup
DIO read not write
– When high, read operation is selected.
– When low, write operation is selected.
SRXRDY
145 O None
Network management port, receive ready. When high, SRXRDY indicates that the network
management port’s RX buffers are empty and the network management port is able to receive
a frame.
STXRDY
144 O None
Network management port, transmit ready. STXRDY indicates that at least one frame buffer is
available to be read by the management CPU.
– It outputs as a 1 if any of the end-of-frame (EOF) bits, start-of-frame (SOF) bits, or one of the
bits in NMTxcontrol is set to 1.
– Otherwise, it outputs 0.