Cypress NoBL CY7C1371D User Manual download pdf (Page 11)

CY7C1371D

CY7C1373D

Document #: 38-05556 Rev. *F Page 11 of 29

IEEE 1149.1 Serial Boundary Scan (JTAG)

The CY7C1371D/CY7C1373D incorporates 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 IO logic levels.

The CY7C1371D/CY7C1373D contains a TAP controller,

instruction register, boundary scan register, bypass register,

and ID register.

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 V

through a pull up resistor. TDO must be

left unconnected. Upon power up, the device is up in a reset

state which does not interfere with the operation of the device.

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. For

information on loading the instruction register, see TAP

Controller State Diagram. TDI is internally pulled up and can

be unconnected if the TAP is unused in an application. TDI is

connected to the most significant 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.)

Performing a TAP Reset

A RESET is performed by forcing TMS HIGH (V

) 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

TAP Controller State Diagram

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

TAP Controller Block Diagram

Bypass Register

Instruction Register

012

Identication Register

012293031 ...

Boundary Scan Register

012..x ...

Selection

Circuitry

TCK

TMS

TAP CONTROLLER

TDI TDO

Selection

Circuitry

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Cypress NoBL CY7C1371D User Manual Page 11

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