How to select JTAG/SPI clock.

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usbbdm
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Joined: Mon Jul 18, 2005 9:33 pm

How to select JTAG/SPI clock.

Post by usbbdm » Mon Apr 19, 2010 10:39 am

I think I have posted before and still get some questions about the JTAG clock.

By default JTAG/SPI clock is set to 12MHz. You can set this in the xml or via command.

"speed 0" 12Mhz
"speed 1" 6MHz.
"speed 2" 3Mhz.

12MHz is reasonably good JTAG clock. It balanced the speed and performance. With this SPI read can be about 900+KB/s. It translate to 7.2Mbit/s. This is not bad consider there are overhead in the SPI protocol.

USB JTAG NT uses USB 2.0 high speed so it can reach 480Mbit/s. In another thread I am thinking raise the JTAG clock to 24Mhz or even 48Mhz. There is some issues with higher JTAG clock. The average user will have problem make good connection (wires length will be limited). But if someone would like to push to the limit and I am happy to do some experiment on the speed.

In the USB standard there is 1.1 and 2.0. In 2.0 there is also high speed and full speed. If one device is only support USB 2.0 full speed, it simply is 12Mbit/s and will not benefit the full USB 2.0 power.

moddog
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Post by moddog » Mon Nov 01, 2010 12:47 am

usbjtag and usbjtags is the same?

CAPONE
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Post by CAPONE » Mon Nov 01, 2010 6:41 am

usbbdm wrote:I think I have posted before and still get some questions about the JTAG clock.

By default JTAG/SPI clock is set to 12MHz. You can set this in the xml or via command.

"speed 0" 12Mhz
"speed 1" 6MHz.
"speed 2" 3Mhz.

12MHz is reasonably good JTAG clock. It balanced the speed and performance. With this SPI read can be about 900+KB/s. It translate to 7.2Mbit/s. This is not bad consider there are overhead in the SPI protocol.

USB JTAG NT uses USB 2.0 high speed so it can reach 480Mbit/s. In another thread I am thinking raise the JTAG clock to 24Mhz or even 48Mhz. There is some issues with higher JTAG clock. The average user will have problem make good connection (wires length will be limited). But if someone would like to push to the limit and I am happy to do some experiment on the speed.

In the USB standard there is 1.1 and 2.0. In 2.0 there is also high speed and full speed. If one device is only support USB 2.0 full speed, it simply is 12Mbit/s and will not benefit the full USB 2.0 power.
Can you and more speeds like
"speed 0"
"speed 1"
"speed 2"
"speed 3"
"speed 4"
To have more Speed Choices?
"If you give a man a fish you feed him for a day. If you teach a man to fish you feed him for a lifetime."

usbbdm
Posts: 8472
Joined: Mon Jul 18, 2005 9:33 pm

Post by usbbdm » Mon Nov 01, 2010 7:32 am

TUNDRA wrote:Can you and more speeds like
"speed 0"
"speed 1"
"speed 2"
"speed 3"
"speed 4"
To have more Speed Choices?
Not with current hardware.

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