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

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

STMS0§

Z

Z

H

OFF

H

H

HARD ERROR¶

H

PTCK

STMS0§

Z

Z

H

OFF

H

H

DISCONNECT

H

PTCK

STMS0§

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.