µTasker Forum
µTasker Forum => NXPTM M522XX, KINETIS and i.MX RT => Topic started by: FAQ on May 16, 2009, 01:30:24 PM
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The schematics of the 52259EVB FlexiBus show the connections between 52259 and the MRAM chip:
52259 RAM chip
D0 --------- D0
D1 --------- D1
D2 --------- D2
D3 --------- D3
D4 --------- D7
D5 --------- D6
D6 --------- D5
D7 --------- D4
The processor D0-D3 match the MRAM chip's D0-D3, then D4-D7 of the processor swaps around on the Ram chip. Is this an error?
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Hi
I think that the reason for the strange looking connection is because it routes better. The EVB has the data lines also connected to 2 data pins and selects the upper/lower byte using A0 – it is this operating in 8 bit data mode (see also http://www.utasker.com/forum/index.php?topic=552.msg2423#msg2423).
52259 RAM chip
D0 --------- D0 – D15
D1 --------- D1 – D14
D2 --------- D2 – D13
D3 --------- D3 – D12
D4 --------- D7 – D11
D5 --------- D6 – D10
D6 --------- D5 – D9
D7 --------- D4 – D8
Since the signals can be up to 80MHz it is important that they are routed cleanly and swapping lines can help. The fact is that you can connect data lines in any order – they don’t need to be D0..D7. What you save at one bit will come out on the same bit so it really doesn’t matter how you name them or connect them. The same is true for the address lines for RAM – for FLASH the address lines are less flexible since the sectors have to remain addressed in defined groups and the data lines are often used for commands (so the bits in the commands have to be at the right place – which can of course be swapped in SW if required).
Regards
Mark