mc68hc908mr24 Freescale Semiconductor, Inc, mc68hc908mr24 Datasheet - Page 314

• Manufacturer Part Number: mc68hc908mr24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Serial Communications Interface Module (SCI)
Advance Information
314
OR — Receiver Overrun Bit
NF — Receiver Noise Flag Bit
FE — Receiver Framing Error Bit
This clearable, read-only bit is set when software fails to read the
SCDR before the receive shift register receives the next character.
The OR bit generates an SCI error CPU interrupt request if the ORIE
bit in SCC3 is also set. The data in the shift register is lost, but the data
already in the SCDR is not affected. Clear the OR bit by reading SCS1
with OR set and then reading the SCDR. Reset clears the OR bit.
Software latency may allow an overrun to occur between reads of
SCS1 and SCDR in the flag-clearing sequence.
the normal flag-clearing sequence and an example of an overrun
caused by a delayed flag-clearing sequence. The delayed read of
SCDR does not clear the OR bit because OR was not set when SCS1
was read. Byte 2 caused the overrun and is lost. The next
flag-clearing sequence reads byte 3 in the SCDR instead of byte 2.
In applications that are subject to software latency or in which it is
important to know which byte is lost due to an overrun, the
flag-clearing routine can check the OR bit in a second read of SCS1
after reading the data register.
This clearable, read-only bit is set when the SCI detects noise on the
PTE1/RxD pin. NF generates an NF CPU interrupt request if the NEIE
bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then
reading the SCDR. Reset clears the NF bit.
This clearable, read-only bit is set when a logic 0 is accepted as the
stop bit. FE generates an SCI error CPU interrupt request if the FEIE
bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set
and then reading the SCDR. Reset clears the FE bit.
Serial Communications Interface Module (SCI)
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
1 = Noise detected
0 = No noise detected
1 = Framing error detected
0 = No framing error detected
MC68HC908MR24
Freescale Semiconductor
Figure 14-11
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shows
Rev. 4.1