MC9S08GB60 Datasheet, PDF (183/290 Pages) Motorola, Inc – Microcontrollers

SCI Registers and Control Bits
OR — Receiver Overrun Flag
OR is set when a new serial character is ready to be transferred to the receive data register (buffer), but
the previously received character has not been read from SCIxD yet. In this case, the new character
(and all associated error information) is lost because there is no room to move it into SCIxD. To clear
OR, read SCIxS1 with OR = 1 and then read the SCI data register (SCIxD).
1 = Receive overrun (new SCI data lost).
0 = No overrun.
NF — Noise Flag
The advanced sampling technique used in the receiver takes seven samples during the start bit and
three samples in each data bit and the stop bit. If any of these samples disagrees with the rest of the
samples within any bit time in the frame, the flag NF will be set at the same time as the flag RDRF gets
set for the character. To clear NF, read SCIxS1 and then read the SCI data register (SCIxD).
1 = Noise detected in the received character in SCIxD.
0 = No noise detected.
FE — Framing Error Flag
FE is set at the same time as RDRF when the receiver detects a logic 0 where the stop bit was expected.
This suggests the receiver was not properly aligned to a character frame. To clear FE, read SCIxS1
with FE = 1 and then read the SCI data register (SCIxD).
1 = Framing error.
0 = No framing error detected. This does not guarantee the framing is correct.
PF — Parity Error Flag
PF is set at the same time as RDRF when parity is enabled (PE = 1) and the parity bit in the received
character does not agree with the expected parity value. To clear PF, read SCIxS1 and then read the
SCI data register (SCIxD).
1 = Parity error.
0 = No parity error.
11.10.5 SCI x Status Register 2 (SCIxS2)
This register has one read-only status flag. Writes have no effect.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 11-10. SCI x Status Register 2 (SCIxS2)
1
Bit 0
0
RAF
0
0
MC9S08GB/GT Data Sheet, Rev. 2.3
Freescale Semiconductor
183