AN2502 Freescale Semiconductor / Motorola, AN2502 Datasheet - Page 4

• Manufacturer Part Number: AN2502
• Description: Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
• Manufacturer: Freescale Semiconductor / Motorola

AN2502/D
4
Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
Because this SCI performs full-duplex operation, it is necessary to have four
separate data registers; two for reception and two for transmission. Each SCI
operation uses two data registers; one is used in the interrupt service routine to
shift in data for reception and shift out data for transmission. These registers
are shown in
Read:
Read:
Read:
Read:
Write:
Write:
Write:
Write:
SCRF — SCI Receiver Full
SCTE — SCI Transmitter Empty
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Figure 5. SCI Transmit Data Register (rSCTDR)
Figure 6. SCI Transmit Shift Register (rSCTSR)
1 = Data available on the receive data register
0 = No data available
1 = Transmit data register is empty
0 = Transmit data register is not empty
Figure 3. SCI Receive Data Register (rSCRDR)
Figure 4. SCI Receive Shift Register (rSCRSR)
Bit 7
RD7
Bit 7
RS7
Bit 7
Bit 7
TD7
TS7
Figure
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RD6
RS6
TD6
TS6
6
6
6
6
3,
Figure
RD5
RS5
TD5
TS5
5
5
5
5
4,
Figure
RD4
RS4
TD4
TS4
4
4
4
4
5, and
RD3
RS3
TD3
TS3
3
3
3
3
Figure
RD2
RS2
TD2
TS2
2
2
2
2
6.
RD1
RS1
TD1
TS1
1
1
1
1
MOTOROLA
Bit 0
RD0
Bit 0
RS0
Bit 0
Bit 0
TD0
TS0