SN54BCT8244A, SN74BCT8244A

SCAN TEST DEVICES

WITH OCTAL BUFFERS

SCBS042E – FEBRUARY 1990 – REVISED JULY 1996

4

POST OFFICE BOX 655303

Terminal Functions

TERMINAL NAME

DESCRIPTION

1A1–1A4, 2A1–2A4

Normal-function data inputs. See function table for normal-mode logic. Internal pullups force these inputs high if left

unconnected.

GND

Ground

1OE, 2OE

Normal-function output-enable inputs. See function table for normal-mode logic. Internal pullups force these inputs

high if left unconnected.

TCK

Test clock. One of four terminals required by IEEE Standard 1149.1-1990. Test operations of the device are

synchronous to TCK. Data is captured on the rising edge of TCK and outputs change on the falling edge of TCK. An

internal pullup forces TCK to a high level if left unconnected.

TDI

Test data input. One of four terminals required by IEEE Standard 1149.1-1990. TDI is the serial input for shifting data

through the instruction register or selected data register. An internal pullup forces TDI to a high level if left unconnected.

TDO

Test data output. One of four terminals required by IEEE Standard 1149.1-1990. TDO is the serial output for shifting

data through the instruction register or selected data register. An internal pullup forces TDO to a high level when it is

not active and is not driven from an external source.

TMS

Test mode select. One of four terminals required by IEEE Standard 1149.1-1990. TMS directs the device through its

TAP controller states. An internal pullup forces TMS to a high level if left unconnected. TMS also provides the optional

test reset signal of IEEE Standard 1149.1-1990. This is implemented by recognizing a third logic level, double high

(VIHH), at TMS.

VCC

Supply voltage

1Y1–1Y4, 2Y1–2Y4

Normal-function data outputs. See function table for normal-mode logic.