MC908QY8CDWE Datasheet, PDF (131/232 Pages) Freescale Semiconductor, Inc – Addendum to MC68HC908QB8, rev. 3

Registers
13.8.5 ESCI Status Register 2
ESCI status register 2 (SCS2) contains flags to signal these conditions:
• Break character detected
• Reception in progress
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
0
0
0
0
0
BKF
RPF
Write:
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure 13-14. ESCI Status Register 2 (SCS2)
BKF — Break Flag Bit
This clearable, read-only bit is set when the ESCI 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 interrupt request. Clear BKF by reading SCS2 with BKF set and then reading the
SCDR. Once cleared, BKF can become set again only after 1s again appear on the RxD pin followed
by another break character.
1 = Break character detected
0 = No break character detected
RPF — Reception in Progress Flag Bit
This read-only bit is set when the receiver detects a 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 ESCI module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
13.8.6 ESCI Data Register
The ESCI 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 ESCI data register.
Bit 7
6
Read: R7
R6
Write: T7
T6
Reset:
5
4
3
2
R5
R4
R3
R2
T5
T4
T3
T2
Unaffected by reset
1
Bit 0
R1
R0
T1
T0
Figure 13-15. ESCI Data Register (SCDR)
R7/T7:R0/T0 — Receive/Transmit Data Bits
Reading SCDR accesses the read-only received data bits, R7:R0.
Writing to SCDR writes the data to be transmitted, T7:T0.
NOTE
Do not use read-modify-write instructions on the ESCI data register.
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor
129