MCU Serial Communications Interface (SCI)
MC1321x Reference Manual, Rev. 1.6
Freescale Semiconductor
18-13
18.9.4
SCI1
Status Register 1 (SCIxS1)
This register has eight read-only status flags. Writes have no effect. Special software sequences (that do
not involve writing to this register) are used to clear these status flags.
Figure 18-8. SCI1
Status Register 1 (SCIxS1)
TDRE — Transmit Data Register Empty Flag
TDRE is set out of reset and when a transmit data value transfers from the transmit data buffer to the
transmit shifter, leaving room for a new character in the buffer. To clear TDRE, read SCIxS1 with
TDRE = 1 and then write to the SCI data register (SCIxD).
1 = Transmit data register (buffer) empty.
0 = Transmit data register (buffer) full.
TC — Transmission Complete Flag
TC is set out of reset and when TDRE = 1 and no data, preamble, or break character is being
transmitted.
1 = Transmitter idle (transmission activity complete).
0 = Transmitter active (sending data, a preamble, or a break).
TC is cleared automatically by reading SCIxS1 with TC = 1 and then doing one of the following:
— Write to the SCI data register (SCIxD) to transmit new data
— Queue a preamble by changing TE from 0 to 1
— Queue a break character by writing 1 to SBK in SCIxC2
RDRF — Receive Data Register Full Flag
RDRF becomes set when a character transfers from the receive shifter into the receive data register
(SCIxD). In 8-bit Mode, to clear RDRF, read SCIxS1 with RDRF = 1 and then read the SCI data
register (SCIxD). In 9-bit Mode, to clear RDRF, read SCIxS1 with RDRF = 1 and then read SCIxD
and the SCI control 3 register (SCIxC3). SCIxD and SCIxC3 can be read in any order, but the flag is
cleared only after both data registers are read.
1 = Receive data register full.
0 = Receive data register empty.
IDLE — Idle Line Flag
IDLE is set when the SCI receive line becomes idle for a full character time after a period of activity.
When ILT = 0, the receiver starts counting idle bit times after the start bit. So if the receive character
is all 1s, these bit times and the stop bit time count toward the full character time of logic high (10 or
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
1
1
0
0
0
0
0
0
= Unimplemented or Reserved
Summary of Contents for freescale semiconductor MC13211
Page 40: ...MC1321x Pins and Connections MC1321x Reference Manual Rev 1 6 2 6 Freescale Semiconductor...
Page 166: ...Modem Modes of Operation MC1321x Reference Manual Rev 1 6 7 22 Freescale Semiconductor...
Page 172: ...Modem Interrupt Description MC1321x Reference Manual Rev 1 6 8 6 Freescale Semiconductor...
Page 186: ...MCU Modes of Operation MC1321x Reference Manual Rev 1 6 10 8 Freescale Semiconductor...
Page 208: ...MCU Memory MC1321x Reference Manual Rev 1 6 11 22 Freescale Semiconductor...
Page 244: ...MCU Parallel Input Output MC1321x Reference Manual Rev 1 6 13 20 Freescale Semiconductor...
Page 288: ...MCU Central Processor Unit CPU MC1321x Reference Manual Rev 1 6 15 20 Freescale Semiconductor...
Page 308: ...MCU Timer PWM TPM Module MC1321x Reference Manual Rev 1 6 17 16 Freescale Semiconductor...
Page 338: ...Inter Integrated Circuit IIC MC1321x Reference Manual Rev 1 6 19 14 Freescale Semiconductor...
Page 372: ...Development Support MC1321x Reference Manual Rev 1 6 21 20 Freescale Semiconductor...
