Sequential (140) GSM

https://johnchihau.blogspot.com/2026/06/blog-post_19.html?m=1

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Ref: https://johnchihau.blogspot.com/2026/06/blog-post_19.html?m=1

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John : See the 2nd picture. There's a data-register called RO.

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Me: Ok.

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John : If R0 chose clock line A,  R0 is on Circuit A.

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Me: Yes, R0 is on circuit A. However,  if the transistor is cut off, indeed,  R0 receive no clock signal.

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John : You are correct.  See the 1st Picture above.  There're 2 Circuits. 

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Me: Ok.

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John: They're Circuit A and Circuit B. Circuit A has its own crystal oscillator.  Circuit B use the oscillator from the GMS antenna. 

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Me: Ok.

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While (The oscillator of the GSM Antenna is running)

{

If (RTS = 1)

{

TXD = Real interrupt. // The transistor is saturated. Clock signal can be received. 

}

else 

{

TXD = Mask interrupt;  // The transistor is cut off. Clock signal can't be received. 

}

}

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John : Before we start,  you might read this article. https://johnchihau.blogspot.com/2026/06/blog-post_19.html?m=1  .

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Me: Ok.

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John : See the code above.  If RTS is at the stage of Mask-Interrupt,  the transmission fail cause no clock signal is received by I/O port.

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Me: However,  does the I/O port still be on Circuit B? 

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John: Yes, I/O port still stay on Circuit B. It is only that the clock signal can't be received cause the transistor is cut-off. In code, we might have something like this,

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1) Subject [I/O]

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2) Circuit [B] <--- I/O port is still on the Circuit B.

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3) Interrupt status [Mask interrupt] <-- Note : The transistor is cut off. No clock signal is received. 

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John : Sometimes,  we dub Masked interrupt as "Sleeping".

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Me: There's a data-field called "Circuit" for R0 or I/O port.

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John : Yes, it's true.