Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
302 Serial Communications Interface Module (SCI) MOTOROLA
Serial Communications Interface Module (SCI)
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the
PTF4/RxD pin. NF generates an NF CPU interrupt r equest 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.
1 = Noise detected
0 = No noise detected
FE — Receiver Framing Error 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.
1 = Framing error detected
0 = No framing error detected
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a par ity error
in incoming data. PE generates a PE CPU interrupt request if the
PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
Figure 14-11. Flag Clearing Sequence
BYTE 1
NORMAL FLAG CLEARING SEQUENCE
READ SCS1
SCRF = 1
READ SCDR
BYTE 1
SCRF = 1
SCRF = 1
BYTE 2 BYTE 3 BYTE 4
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 2
SCRF = 0
READ SCS1
SCRF = 1
OR = 0
SCRF = 1
SCRF = 0
READ SCDR
BYTE 3
SCRF = 0
BYTE 1
READ SCS1
SCRF = 1
READ SCDR
BYTE 1
SCRF = 1
SCRF = 1
BYTE 2 BYTE 3 BYTE 4
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 3
DELAYED FLAG CLEARING SEQUENCE
OR = 1
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 0
OR = 0