Datasheet

SN54LVT8996, SN74LVT8996
3.3-V 10-BIT ADDRESSABLE SCAN PORTS
MULTIDROP-ADDRESSABLE IEEE STD 1149.1 (JTAG) TAP TRANSCEIVERS
SCBS686A – APRIL 1997 – REVISED DECEMBER 1999
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description (continued)
Whether the connected status is achieved by use of shadow protocol or by use of BYP, this status is indicated
by a low level at the connect (CON) output. Likewise, when the secondary TAP is disconnected from the primary
TAP, the CON output is high.
The SN54LVT8996 is characterized for operation over the full military temperature range of –55°C to 125°C.
The SN74LVT8996 is characterized for operation from –40°C to 85°C.
FUNCTION TABLE
INPUTS
SHADOW-PROTOCOL
OUTPUTS
PRIMARY-TO-SECONDARY
BYP PTRST
RESULT
†
STRST STCK STMS STDO PTDO CON
CONNECT STATUS
L L — L PTCK H
‡
PTDI STDI L BYP/TRST
‡
L H—H PTCK PTMS PTDI STDI L BYP
H L—L PTCK H Z Z H TRST
H H RESET H PTCK H Z Z H RESET
H H MATCH H PTCK PTMS PTDI STDI L ON
H H NO MATCH H PTCK STMS
0
§
Z Z H OFF
H H HARD ERROR
¶
H PTCK STMS
0
§
Z Z H OFF
H H DISCONNECT H PTCK STMS
0
§
Z Z H OFF
H H TEST SYNCHRONIZATION H PTCK PTMS PTDI Z L MULTICAST
†
Shadow protocols are received serially via PTCK and PTDI and acknowledged serially via PTCK and PTDO under certain conditions in which
PTMS is static low or static high (see shadow protocol). The result shown here follows any required acknowledgment.
‡
In normal operation of IEEE Std 1149.1-compliant architectures, it is recommended that TMS be high prior to release of TRST
. The BYP/TRST
connect status ensures that this condition is met at STMS regardless of the applied PTMS. Also, it is recommended that STMS be kept high for
a minimum duration of 5 PTCK cycles following assertion of PTRST
, either by maintaining PTRST low or by setting PTMS high. This ensures
that ICs both with and without TRST inputs are moved to their Test-Logic-Reset TAP states. It is expected that in normal application, this condition
occurs only when BYP
is fixed at the low state. In such case, upon release of PTRST, the ASP immediately resumes the BYP connect status.
§
STMS level before indicated steady-state conditions were established
¶
The shadow protocol is well defined. Some variations in the protocol are tolerated (see protocol errors). Those that are not tolerated produce
protocol result HARD ERROR and cause disconnect as indicated.