Cypress Semiconductor CY7C1441AV33 User Manual download pdf (Page 13)

CY7C1441AV33

CY7C1443AV33

CY7C1447AV33

Document #: 38-05357 Rev. *F Page 12 of 31

IEEE 1149.1 Serial Boundary Scan (JTAG)

The CY7C1441AV33/CY7C1443AV33/CY7C1447AV33 incor-

porates a serial boundary scan test access port (TAP). This

part is fully compliant with 1149.1. The TAP operates using

JEDEC-standard 3.3V or 2.5V I/O logic levels.

The CY7C1441AV33/CY7C1443AV33/CY7C1447AV33

contains a TAP controller, instruction register, boundary scan

Disabling the JTAG Feature

It is possible to operate the SRAM without using the JTAG

feature. To disable the TAP controller, TCK must be tied LOW

) to prevent clocking of the device. TDI and TMS are inter-

nally pulled up and may be unconnected. They may alternately

be connected to VDD through a pull-up resistor. TDO should be

left unconnected. Upon power-up, the device will come up in

a reset state which will not interfere with the operation of the

device.

TAP Controller State Diagram

The 0/1 next to each state represents the value of TMS at the

rising edge of TCK.

Test Access Port (TAP)

Test Clock (TCK)

The test clock is used only with the TAP controller. All inputs

are captured on the rising edge of TCK. All outputs are driven

from the falling edge of TCK.

Test MODE SELECT (TMS)

The TMS input is used to give commands to the TAP controller

and is sampled on the rising edge of TCK. It is allowable to

leave this ball unconnected if the TAP is not used. The ball is

pulled up internally, resulting in a logic HIGH level.

Test Data-In (TDI)

The TDI ball is used to serially input information into the

registers and can be connected to the input of any of the

registers. The register between TDI and TDO is chosen by the

instruction that is loaded into the TAP instruction register. TDI

is internally pulled up and can be unconnected if the TAP is

unused in an application. TDI is connected to the most signif-

icant bit (MSB) of any register. (See Tap Controller Block

Diagram.)

Test Data-Out (TDO)

The TDO output ball is used to serially clock data-out from the

registers. The output is active depending upon the current

state of the TAP state machine. The output changes on the

falling edge of TCK. TDO is connected to the least significant

bit (LSB) of any register. (See Tap Controller State Diagram.)

TAP Controller Block Diagram

Performing a TAP Reset

A RESET is performed by forcing TMS HIGH (VDD) for five

rising edges of TCK. This RESET does not affect the operation

of the SRAM and may be performed while the SRAM is

operating.

At power-up, the TAP is reset internally to ensure that TDO

comes up in a High-Z state.

TAP Registers

Registers are connected between the TDI and TDO balls and

allow data to be scanned into and out of the SRAM test

circuitry. Only one register can be selected at a time through

the instruction register. Data is serially loaded into the TDI ball

on the rising edge of TCK. Data is output on the TDO ball on

the falling edge of TCK.

Instruction Register

Three-bit instructions can be serially loaded into the instruction

TDI and TDO balls as shown in the Tap Controller Block

Diagram. Upon power-up, the instruction register is loaded

with the IDCODE instruction. It is also loaded with the IDCODE

instruction if the controller is placed in a reset state as

described in the previous section.

TEST-LOGIC

RESET

RUN-TEST/

IDLE

SELECT

DR-SCAN

SELECT

IR-SCAN

CAPTURE-DR

SHIFT-DR

CAPTURE-IR

SHIFT-IR

EXIT1-DR

PAUSE-DR

EXIT1-IR

PAUSE-IR

EXIT2-DR

UPDATE-DR

EXIT2-IR

UPDATE-IR

1 1

0 0

1 1

0 0

1 0

Bypass Register

Instruction Register

012

Identification Register

012293031 ...

Boundary Scan Register

012..x ...

election

Circuitr

Selection

Circuitry

TCK

MS TAP CONTROLLER

TDI TD

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