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Wednesday, April 18, 2007

Bit manipulation using opcodes

How to update a bit using opcode
This guide will show you how to manipulate bits in SEEM. Before you read on, you must have already read this guide about motorola opcode. As you can see from the "motorola opcode" guide, we can only read/write bytes, but not bits. We have to do some calculation, in order to change only the bits we want to change.

I think the best way to explain it is by example. Let's say we want to do the following seem edit:

option to switch storage device (discovered by Yuet)
SEEM 0032-0001 offset 9F bit 3:
on = switch to phone memory/memory card directly in list, java apps will be installed in card when "install new apps"
off = press menu key to see "switch storage device" option, will prompt to select storage device when "install new apps"


1. to get the value of the offset 9F in SEEM 0032-0001, we use the following opcode:

2. The value we get is "c8", which is a hex value. It is 200 in dec value. We try to decode "200" using this formula:
200 = bit0 x 1 + bit1 x 2 + bit2 x 4 + bit3 x 8 + bit4 x 16 + bit5 x 32 + bit6 x 64 + bit7 x 128

What we get is:
200 = 0 x 1 + 0 x 2 + 0 x 4 + 1 x 8 + 0 x 16 + 0 x 32 + 1 x 64 + 1 x 128

so we can see in this offset, bit 3, 6 & 7 are on. In this example, we want to turn off bit 3 to enable the "switch storage device" option, so we change value of bit3 to 0 in the formula. We get:
0 x 1 + 0 x 2 + 0 x 4 + 0 x 8 + 0 x 16 + 0 x 32 + 1 x 64 + 1 x 128 = 192

192 is the value we are going to write to the offset 9F.

3. We write the value 192 to offset 9F in SEEM 0032-0001 using the following opcode:

4. Reboot the phone using opcode 34, and it is done.

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4:29 AM, April 19, 2007 Deathek said...

Hi Yuet! Your MP for L7 is simply the best! You've done something great :) I;ve got only 1 question:
How to make my phone (SLVR L7 Yor MP 2.1) compatible with audio adaptor? Charging port->mini jack (something like this one: ). How to make it work? I heared that these things won't work with the Moto L7. Is it true? Thanks in advance and regards :) (sorry for any mistakes, I tried my best ;p I'm polish and still learning english;])

9:46 AM, April 19, 2007 Yuet said...

deathek, I think it should work, but I have not tried it myself.

2:52 PM, April 19, 2007 Deathek said...

Ok thanks :) I tried one so far and it doesn't work, but I'll try another one and check. I read yesterday that for example V3xx has another pin arrangement than L7 and that's the cause most adaptors don't work (they are beeing created for V3xx phones and sold as compatible with L7). So people, beware! ;) Web