TRIPLEPORTPHY(PHYSICALLAYER)FOR25.6
AND 51.2 MBPS ATM NETWORKS
IDT77V1253
TABLE 1 — SIGNAL DESCRIPTIONS
LINE SIDE SIGNALS
SIGNAL NAME
RX0+,-
PIN NUMBER
139, 138
133, 132
121, 120
4, 3
I/O
In
SIGNAL DESCRIPTION
Port 0 positive and negative receive differential input pair.
Port 1 positive and negative receive differential input pair.
Port 2 positive and negative receive differential input pair.
Port 0 positive and negative transmit differential output pair.
Port 1 positive and negative transmit differential output pair.
Port 2 positive and negative transmit differential output pair.
RX1+,-
In
RX2+,-
In
TX0+,-
Out
Out
Out
TX1+,-
144, 143
110, 109
TX2+,-
UTILITY BUS SIGNALS
I/O
SIGNAL NAME
PIN NUMBER
SIGNAL DESCRIPTION
AD[7:0]
101, 100, 99, 98,
96, 95, 94, 93
In/Out
Utility bus address/data bus. The address input is sampled on the falling
edge of ALE. Data is output on this bus when a read is performed. Input
data is sampled at the completion of a write operation.
ALE
91
In
Utility bus address latch enable. Asynchronous input. An address on the
AD bus is sampled on the falling edge of ALE. ALE may be either high
low when the AD bus is being used for data.
90
89
In
In
Utility bus asynchronous chip select. CS must be asserted to read or
CS
RD
write an internal register. It may remain asserted at all times if desired.
Utility bus read enable. Active low asynchronous input. After latching
an address, a read is performed by deasserting WR and asserting
RD and CS.
88
In
Utility bus write enable. Active low asynchronous input. After latching
an address, a write is performed by deasserting RD, placing data
on the AD bus, and asserting WR and CS. Data is sampled.
WR
MISCELLANEOUS SIGNALS
I/O
SIGNAL NAME
PIN NUMBER
103
SIGNAL DESCRIPTION
DA
In
Reserved signal. This input must be connected to logic low.
DNC
12, 82, 105, 106
Out
Do Not Connect. Do not connect these pins to anything external to the
chip. They must remain open.
85
Out
Interrupt. INT is an open-drain output, driven low to indicate an interrupt.
Once low, INT remains low until the interrupt status in the appropriate
interrupt Status Register is read. Interrupt sources are programmable
via the interrupt Mask Registers.
INT
MA
MB
114
115
6
In
In
In
In
Reserved signal. This input must be connected to logic low.
Reserved signal. This input must be connected to logic low.
Reserved signal. This input must be connected to logic high.
MM
MODE[1:0]
7, 8
Mode Selects. They determine the configuration of the PHY/ATM
interface. 00 = UTOPIA Level 2. 01 = UTOPIA Level 1. 10 = DPI.
11 is reserved.
OSC
126
87
In
In
TTL line rate clock source, driven by a 100 ppm oscillator. 32 MHz
for 25.6 Mbps; 64 MHz for 51.2 Mbps.
Reset. Active low asynchronous input resets all control logic, counters
and FIFOs. A reset must be performed after power up prior to normal
operation of the part.
RST
Receive LED drivers. Driven low for 223 RCLK or DPICLK cycles,
beginning with RXSOC when that port receives a good (non-null and
non-errored) cell. Drives 8 mA both high and low. One per port.
RXLED[2:0]
81, 80, 79
Out
4781 tbl 01
3