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IBM2520L8767
IBM Processor for ATM Resources
atmrm.chapt02.01
08/27/99
NPBUS
Page 27 of 553
1
PBSCLK
Output
Clock for the I
2
C serial
EPROM accesses.
1
PBSDATA
Output or
Data
This is the data bit that connects to the external serial EPROM to
read from or write to. It must have a pullup resistor attached and
supports the I
2
C protocol. The range of suported serial EPROM is
from 256 to 2K bytes. After reset, the IBM2520L8767 will start
accessing the optional on-card serial EPROM and do the chip ini-
tialization function. If this chip is pulled down (or no pullup), the
IBM2520L8767 will assume that no serial EPROM is attacted and
will go try to fetch from a parallel EPROM.
1
PBRNWRT
Output
Read or Write
This pin allows the IBM2520L8767 to read from or write to internal
registers of the PHY parts. This signal acts as the write strobe
when talking to PMC-Sierra chips such as the Suni-Lite .
1
PBRDRDY
S/T/S
1
This pin allows the IBM2520L8767 to read from or write into inter-
nal registers of the PHYs by acting as a data acknowledge signal
from the memory slaves.
8
PBDATA(7-0)
Input or
Output
The PB-Bus is an eight-bit wide bidirectional data bus used to inter-
face the PHYs to the IBM2520L8767 When a data transfer is not
happening, the lower four bits act as: MLED(3-0) - four control pins
that, under register bit control, can drive general status to LED
devices.
1
PBINTRA
Input
This input from PHY A is an attention line that, when LOW, indi-
cates that one or more unmasked flags are set in the status regis-
ters of PHY 1
If additional PHY parts are added, they should also dot their inter-
rupt line onto this input.
1
PBPHYRST
Output
Implements the network
safety features of the
device
This signal is the ORed value of RESET and all of the status bits
that cause the IBM2520L8767 to stop transferring data. It is
asserted for a pulse, and then removed. This signal is asserted
low.
NPBUS Pin Descriptions
(Page 2 of 2)
Quantity
Pin Name
Input/Output
Pin Function
Pin Description
1. S/T/S = a sustained tri-state pin owned and driven by one and only one agent at a time. The agent that drives the s/t/s pin low must
drive it high for at least one clock before letting it float. A new agent cannot start driving a s/t/s signal any sooner that one clock
after the previous owner tri-states it. A pullup is required to sustain the inactive state until another agent drives it, and must be pro-
vided by the central resource.