MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 275

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

MC68HC708AS48
MOTOROLA
—
Rev. 4.0
SCRF — SCI Receiver Full Bit
IDLE — Receiver Idle Bit
OR — Receiver Overrun Bit
This clearable, read-only bit is set when the data in the receive shift
register transfers to the SCI data register. SCRF can generate an SCI
receiver CPU interrupt request. In normal operation, clear the SCRF
bit by reading SCS1 with SCRF set and then reading the SCDR.
Reset clears SCRF.
This clearable, read-only bit is set when 10 or 11 consecutive logic 1s
appear on the receiver input. IDLE generates an SCI error CPU
interrupt request if the ILIE bit in SCC2 is also set and the DMARE bit
in SCC3 is clear. Clear the IDLE bit by reading SCS1 with IDLE set
and then reading the SCDR. After the receiver is enabled, it must
receive a valid character that sets the SCRF bit before an idle
condition can set the IDLE bit. Also, after the IDLE bit has been
cleared, a valid character must again set the SCRF bit before an idle
condition can set the IDLE bit. Reset clears the IDLE 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.
1 = Received data available in SCDR
0 = Data not available in SCDR
1 = Receiver input idle
0 = Receiver input active (or idle since the IDLE bit was cleared)
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Serial Communications Interface (SCI)
Serial Communications Interface (SCI)
Figure 17-13
Advance Information
I/O Registers
shows
275