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14.4.6 Additional SCI functions
The following sections describe additional SCI functions.
14.4.6.1 8- and 9-bit data modes
The SCI system, transmitter and receiver, can be configured to operate in 9-bit data mode
by setting SCI_C1[M]. In 9-bit mode, there is a ninth data bit to the left of the most
significant bit of the SCI data register. For the transmit data buffer, this bit is stored in T8
in SCI_C3. For the receiver, the ninth bit is held in SCI_C3[R8].
For coherent writes to the transmit data buffer, write to SCI_C3[T8] before writing to
SCI_D.
If the bit value to be transmitted as the ninth bit of a new character is the same as for the
previous character, it is not necessary to write to SCI_C3[T8] again. When data is
transferred from the transmit data buffer to the transmit shifter, the value in SCI_C3[T8]
is copied at the same time data is transferred from SCI_D to the shifter.
The 9-bit data mode is typically used with parity to allow eight bits of data plus the parity
in the ninth bit, or it is used with address-mark wake-up so the ninth data bit can serve as
the wakeup bit. In custom protocols, the ninth bit can also serve as a software-controlled
marker.
14.4.6.2 Stop mode operation
During all stop modes, clocks to the SCI module are halted.
No SCI module registers are affected in Stop3 mode.
The receive input active edge detect circuit remains active in Stop3 mode. An active edge
on the receive input brings the CPU out of Stop3 mode if the interrupt is not masked
(SCI_BDH[RXEDGIE] = 1).
Because the clocks are halted, the SCI module resumes operation upon exit from stop,
only in Stop3 mode. Software must ensure stop mode is not entered while there is a
character (including preamble, break and normal data) being transmitted out of or
received into the SCI module, that means SCI_S1[TC] =1, SCI_S1[TDRE] = 1, and
SCI_S2[RAF] = 0 must all meet before entering stop mode.
Functional description
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
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Summary of Contents for MC9S08PA4
Page 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
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Page 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Page 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Page 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Page 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Page 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Page 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Page 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Page 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
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