Fujitsu FR81S ユーザーズマニュアル
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
5. Operation of UART
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
164
Transmission Operation by External Trigger
If the synchronous transmission is enabled (SACSR:TSYNE="1"), the external trigger is enabled
(SACSR:TRGE="1"), the timer comparison register (STMCR) is set to (0000)H, the transmission is
enabled (SCR:TXE="1"), and the valid data exists (SSR:TDRE="0"), the transmission operation by the
external trigger starts.
Starting the transmission operation by the external trigger operates as shown below:
1. If the edge of the external trigger which is set with the trigger selection bit (SACSR:TRG1, 0) is
detected, the transmission operation starts immediately. It continues to send the transmission data while
the transmission bus idle flag (SSR:TB1) is "0".
2. If the transmission data is written to the transmission data register (TDR) after the transmission bus idle
(SSR:TB1="1"), the transmission operation starts when the edge of the external trigger which is set
with the trigger selection bit (SACSR:TRG1, 0) is detected.
Figure 5-17 Transmission Operation by External Trigger (TRG1="0", TRG0="1")
0
STMR
STMCR
External
trigger
trigger
0
10
STMCR
TINT
1
st
Byte
2
nd
Byte
TDRE
Transmission
data
data
Output transmission data when there is a
match between STMR and STMCR
match between STMR and STMCR
No data transmission because
there is no data (TDRE=0)
there is no data (TDRE=0)
3
rd
Byte
L
TDR RW
TBI
4
th
Byte
Output transmission data when there is a
match between STMR and STMCR
match between STMR and STMCR
TBYTE0
2
1
0
2
1
0
2
2
Transmissions
counter*A
counter*A
Load
Load
*A:Internal counter to be count transmission bytes
If the edge of the external trigger which is set with the trigger selection bit (SACSR:TRG1, 0) is detected
during the transmission operation by the external trigger in progress under the following conditions, the
transmission will not start.
⋅
When transmission is disabled (SCR:TXE="0")
⋅
When there is no valid data in the transmission data register (SSR:TDRE)
MB91520 Series
MN705-00010-1v0-E
1477