Sun Microelectronics
338
UltraSPARC User’s Manual
E.2.2 UltraSPARC Data Buffer (UDB) Pins
Table E-2
UltraSPARC Data Buffer (UDB) Pins
Symbol
Type
Name and Function
SYSDATA<63:0>
I/O
Connects the UDB chip to the system data interconnect. Two UDB chips are required.
Each UDB chip handles half of the 128-bit system data interconnect.
SYSECC<7:0>
I/O
ECC check bits for SYSDATA. ECC will be generated and driven by the UDB chip for
SYSDATA transfers from the UDB, and checked if UDB is the receiver.
S_REPLY<3:0>
I
Reply packet from the system. Used by the UDB for initiating data transfers between
the system and the data buffer chips.
SC_DATA_STALL
I
This signal is asserted to hold UDB output data to the system or signal the delay in
arrival of input data from the system.
SC_ECC_VALID
I
Asserted by the system when the ECC of incoming SYSDATA should be checked.
SYSID<4:0>
I
These pins set the five-bit system node ID of the UDB chip and associated
UltraSPARC from the system interconnect.
SYSCLKA, SYSCLKB
I
These are buffered differential versions of the PECL system clock.
EDATA<63:0>
I/O
Connects the UDB with the E-Cache rams and UltraSPARC. On E-Cache misses,
these pins drive data to the E-Cache rams from one of the UDB buffers. On E-Cache
write-backs, these pins input data from the E-Cache rams into one of the UDB buff-
ers. Uncacheable loads and stores transfer data directly between UltraSPARC and the
UDB chips. These pins are also used to transfer data to control/status registers on the
UDB chip.
EDPAR<7:0>
I/O
Byte parity for EDATA. Odd parity is driven for all EDATA transfers from the UDB,
and checked if UDB is the receiver. EDPAR<0> serves as the parity for EDATA<7:0>.
UDB_CE
O
This pin is asserted when the UDB detects a correctable ECC error on data received
from the interconnect, i.e. a single bit error.
UDB_UE
O
This pin is asserted when the UDB detects an uncorrectable ECC error on data
received from the interconnect.
UDB_CNTL<4:0>
I
These pins are used by UltraSPARC to tell the UDB which internal buffer or register
to access and when to drive and receive data on the external cache data bus.
UDB_H
I
This pin is asserted high for UDB_H (the UDB chip for EDATA<127:64>) and to zero
for UDB_L (the UDB chip for the least significant 72 bits).
EPD
I
Asserted by UltraSPARC to cause the UDB to enter power-down mode.
RESET_L
I
Asserted asynchronously for POR (power-on) resets. Deasserted synchronous to sys-
tem clock. Active low.
TDO
O
IEEE 1149.1 test data output. A three-state signal driven only when the TAP control-
ler is in the shift-DR state.
TDI
I
IEEE 1149.1 test data input.
TCK
I
IEEE 1149.1 test clock input. If this pin is not connected to a clock source then
TRST_L must be asserted during POR.
TMS
I
IEEE 1149.1 test mode select input. This pin should externally be pulled to logic one
when not driven.
TRST_L
I
IEEE 1149.1 test reset input (active low). This pin should externally be pulled to logic
one when not driven.
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