MC908JL16CFAE FREESCALE [Freescale Semiconductor, Inc], MC908JL16CFAE Datasheet - Page 106

• Manufacturer Part Number: MC908JL16CFAE
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Serial Communications Interface (SCI)
7.8.5 SCI Status Register 2
SCI status register 2 contains flags to signal the following conditions:
BKF — Break Flag Bit
RPF — Reception in Progress Flag Bit
7.8.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit
shift registers. Reset has no effect on data in the SCI data register.
R7/T7–R0/T0 — Receive/Transmit Data Bits
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This clearable, read-only bit is set when the SCI detects a break character on the RxD pin. In SCS1,
the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is cleared. BKF
does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set and then reading
the SCDR. Once cleared, BKF can become set again only after logic 1s again appear on the RxD pin
followed by another break character. Reset clears the BKF bit.
This read-only bit is set when the receiver detects a logic 0 during the RT1 time period of the start bit
search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start
bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. Polling
RPF before disabling the SCI module or entering stop mode can show whether a reception is in
progress.
Reading the SCDR accesses the read-only received data bits, R[7:0]. Writing to the SCDR writes the
data to be transmitted, T[7:0]. Reset has no effect on the SCDR.
1 = Break character detected
0 = No break character detected
1 = Reception in progress
0 = No reception in progress
Break character detected
Incoming data
Address:
Address:
Reset:
Reset:
Read:
Read:
Write:
Write:
Do not use read/modify/write instructions on the SCI data register.
$0017
$0018
Bit 7
Bit 7
R7
T7
0
Figure 7-14. SCI Status Register 2 (SCS2)
= Unimplemented
Figure 7-15. SCI Data Register (SCDR)
R6
T6
6
0
6
MC68HC908JL16 Data Sheet, Rev. 1.1
R5
T5
5
0
5
NOTE
Unaffected by reset
R4
T4
4
0
4
R3
T3
3
0
3
R2
T2
2
0
2
BKF
R1
T1
1
0
1
Freescale Semiconductor
Bit 0
RPF
Bit 0
R0
T0
0