Data Transmission - Epson S1C31D50 Technical Manual

Cmos 32-bit single chip
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13.5.2 Data Transmission

A data sending procedure and the UART3 Ch.n operations are shown below. Figures 13.5.2.1 and 13.5.2.2 show a
timing chart and a flowchart, respectively.
Data sending procedure
1. Check to see if the UART3_nINTF.TBEIF bit is set to 1 (transmit buffer empty).
2. Write transmit data to the UART3_nTXD register.
3. Wait for a UART3 interrupt when using the interrupt.
4. Repeat Steps 1 to 3 (or 1 and 2) until the end of transmit data.
UART3 data sending operations
The UART3 Ch.n starts data sending operations when transmit data is written to the UART3_nTXD register.
The transmit data in the UART3_nTXD register is automatically transferred to the shift register and the
UART3_nINTF.TBEIF bit is set to 1 (transmit buffer empty).
The USOUTn pin outputs a start bit and the UART3_nINTF.TBSY bit is set to 1 (transmit busy). The shift reg-
ister data bits are then output successively from the LSB. Following output of MSB, the parity bit (if parity is
enabled) and the stop bit are output.
Even if transmit data is being output from the USOUTn pin, the next transmit data can be written to the
UART3_nTXD register after making sure the UART3_nINTF.TBEIF bit is set to 1.
If no transmit data remains in the UART3_nTXD register after the stop bit has been output from the USOUTn
pin, the UART3_nINTF.TBSY bit is cleared to 0 and the UART3_nINTF.TENDIF bit is set to 1 (transmission
completed).
USOUTn
UART3_nINTF.TBEIF
UART3_nINTF.TBSY
UART3_nINTF.TENDIF
Software operations
Read the UART3_nINTF.TBEIF bit
S1C31D50/D51 TECHNICAL MANUAL
(Rev. 2.00)
st D0 D1 D2 D3 D4 D5 D6 D7 p sp st D0 D1
Data (W) → UART3_nTXD
Data (W) → UART3_nTXD
Figure 13.5.2.1 Example of Data Sending Operations
Data transmission
UART3_nINTF.TBEIF = 1 ?
YES
Write transmit data to
the UART3_nTXD register
Transmit data remained?
NO
End
Figure 13.5.2.2 Data Transmission Flowchart
Seiko Epson Corporation
D7 p sp
NO
YES
Wait for an interrupt request
(UART3_nINTF.TBEIF = 1)
13 UART (UART3)
st D0 D1
D7 p sp
Data (W) → UART3_nTXD
1 (W) → UART3_nINTF.TENDIF
(st: start bit, sp: stop bit, p: parity bit)
13-5

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