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AR# 2144

XC9500 JTAG - How long does it take to carry out various JTAG instructions in 9500 CPLDs?

Description

General Description:

How long do the various JTAG instructions take to execute:

Users programming 9500 devices with a micro processor have

wanted to know how long to wait for different jtag instructions

to complete execution.

1. Are these operations self-timed?

2. How long does his processor have to wait between cycles?

3. What is the range of delay From the shortest time to the

longest time? Is there a maximum period?

Solution

Each operation has a shifting time associated with shifting in

the bits of the instruction and the associated data. This time

is dependent on the method used to access the TAP. The maximum

TAP speed of the xc9500 is typically 10MHz.

The speed at which you operate your boundary-scan chain will be

determined by the slowest part on the chain.

The instruction register length for the xc9500 is 8 bits and

the data length varies as per the instruction. The differing

data register sizes can be extracted from the device BSDL

files. They range from 1 bit (the BYPASS register) to several

hundred bits (the BOUNDARY-SCAN register) in length.

The programming (FPGM, FPGMI) and erase (FERASE, FBULK)

instructions also have a "Flash" or "latency" time associated

with them. This is time to be spent in the Run-Test/Idle state

while waiting for the operation to actually complete.

For program this time is typically 160 usec.

For erase this time is typically 1.3 seconds.

These flash operations are self-timed and require no pulsing of

TCK (although TCK can pulse). The operations shut off

automatically if you wait longer than the required time.

Leaving Run-Test/Idle prematurely terminates the operation in

progress.

There is no minimum or maximum range specified. The times are

set at the factory to guarantee completion of the specified

operation.

Please note all these flash times are encoded in the SVF file

as described in (Xilinx XAPP058). As well, all the bits to be shifted

into the part are included in the SVF file in the correct order

to effect the required operations.

AR# 2144
Date Created 08/21/2007
Last Updated 12/15/2012
Status Active
Type General Article