HD643303x Hitachi, HD643303x Datasheet - Page 367

• Manufacturer Part Number: HD643303x
• Description: Hitachi Microcomputer
• Manufacturer: Hitachi

In transmitting serial data, the SCI operates as follows.
•
•
Serial transmit data is transmitted in the following order from the TxD pin:
•
Figure 11-11 shows an example of SCI transmit operation using a multiprocessor format.
Figure 11-11 Example of SCI Transmit Operation (8-Bit Data with Multiprocessor Bit and
Serial
data
TDRE
TEND
The SCI monitors the TDRE flag in SSR. When the TDRE flag is cleared to 0 the SCI
recognizes that TDR contains new data, and loads this data from TDR into TSR.
After loading the data from TDR into TSR, the SCI sets the TDRE flag to 1 and starts
transmitting. If the TIE bit in SCR is set to 1, the SCI requests a transmit-data-empty interrupt
(TXI) at this time.
— Start bit:
— Transmit data:
— Multiprocessor bit: One multiprocessor bit (MPBT value) is output.
— Stop bit:
— Mark state:
The SCI checks the TDRE flag when it outputs the stop bit. If the TDRE flag is 0, the SCI
loads data from TDR into TSR, outputs the stop bit, then begins serial transmission of the
next frame. If the TDRE flag is 1, the SCI sets the TEND flag in SSR to 1, outputs the stop
bit, then continues output of 1 bits in the mark state. If the TEIE bit is set to 1 in SCR, a
transmit-end interrupt (TEI) is requested at this time.
1
TXI
request
Start
bit
0
TXI interrupt handler
writes data in TDR and
clears TDRE flag to 0
D0
One 0 bit is output.
7 or 8 bits are output, LSB first.
One or two 1 bits (stop bits) are output.
Output of 1 bits continues until the start bit of the next transmit data.
D1
1 frame
Data
D7
0/1
One Stop Bit)
Multi-
processor
bit
TXI
request
Stop
bit
352
1
Start
bit
0
D0
D1
Data
D7
0/1
Multi-
processor
bit
TEI request
Stop
bit
1
Idle (mark)
state
1