UCD3138: Questions of UCD3138 reset condition

If you're not using the bootloader on the UCD3138 and UCD3138A, it should take about 10 ms for the UCD boot ROM to initialize the part and verify the checksum. During this time, it will typically draw 5 to 10 mA less because running from ROM is a bit more efficient that running from flash.

So you can use chip current as another way to try to see what is happening if you don't have an I/O line set up.

Then there will be additional time depending on where it hits the code which resets it.

On the UCD3138064, the timing is more complicated. For bootloader in the first 2K, it will be very fast, like the UCD3138. For a checksum in the first 32K, it will be about 10 ms, just like the 3138. If the checksum is in the second 2K boot space, it will be a bit longer. If the checksum is in the second 32K, or the whole 64K, it will be about 20 msec, because it will have to go througth the whole 64K

On the UCD3138128, A64, and 128A, we put in a faster checksum calculation that reads a word at a time instead of a byte so that we can do the whole checksum on the 128K flash in 10 ms or so. So everything else speeds up as well by a factor of about 4. There are still 5 cases:

2K bootflash - fast
first 32K - around 3 ms
first 64K - around 6 ms
second 64K, all 128K - around 10 ms.

Reading a word at a time, we went to an 8 byte checksum on these devices instead of a 4 byte one.

Probably too much information, but a handy reference.