WizWom wrote:JTAG is not "obscured with robust countermeasures" - I have seen chips designed to operate as memory normally, but when a specific sequence of addresses was accessed, to enter a special mode.
WizWom wrote:JTAG is not "obscured with robust countermeasures" - I have seen chips designed to operate as memory normally, but when a specific sequence of addresses was accessed, to enter a special mode.
WizWom wrote:JTAG is not "obscured with robust countermeasures" - I have seen chips designed to operate as memory normally, but when a specific sequence of addresses was accessed, to enter a special mode.
G=C800:5, anyone?
Um... that's an "execute at address" command.
Sure is. Used to use it a lot - and it was an 'undocumented' command as far as the end user knew. It threw an MFM hard drive controller into a mode that low-level formatted a drive.
The normal user didn't know it was there, didn't know how to get at it, and wouldn't have known what to with it if they had.
And I wouldn't be surprised if there were security folk at the time who heard about it, and wanted it disabled on machines their company bought for fear their competitors could access it remotely.
Ah, 20mb drives... they were so large, how would we ever fill them up?
When opinion and reality conflict - guess which one is going to win in the long run.
You can't remotely hack a JTAG, you have to be physically touching the PCB and soldiering wires to the proper pins to make the RS-232 connection work.
JTAG does not use RS-232 levels or UART coding.
Roughly it is a clock, data in, data out, power, ground, and a reset. Levels are what ever levels the chip operates at. ie 1.8, 2.5, 3.3, 5 volts.
I'm referring to the external interfaces, if they bother putting one there (external as in port on side of box). Ones I've seen are using RS-232 9-pin as their connector with some sort of front end command interface.
You can't remotely hack a JTAG, you have to be physically touching the PCB and soldiering wires to the proper pins to make the RS-232 connection work.
JTAG does not use RS-232 levels or UART coding.
Roughly it is a clock, data in, data out, power, ground, and a reset. Levels are what ever levels the chip operates at. ie 1.8, 2.5, 3.3, 5 volts.
I'm referring to the external interfaces, if they bother putting one there (external as in port on side of box). Ones I've seen are using RS-232 9-pin as their connector with some sort of front end command interface.
A "RS-232 9-pin" is called a DB-9 in the trade.
Engineering is the art of making what you want from what you can get at a profit.
