Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
4. Registers
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
54
4.3.4.
Receive Data Register/Transmit Data Register:
RDR/TDR
RDR/TDR
The receive data register and transmit data register are located within the same addresses. When read, it
functions as the receive data register and when written, it functions as the transmit data register. When FIFO
is enabled, the address of RDR/TDR will be the address for reading/writing FIFO.
Read
RDR1n-0n(n=0 to 11) : Address Base addr + 04
H
(Access: Byte, Half-word,
Word)
31
30
29
28
27
26
25
24
bit
D31
D30
D29
D28
D27
D26
D25
D24
0
0
0
0
0
0
0
0
Initial value
R,W
R,W
R,W
R,W
R,W
R,W
R,W
R,W
Attribute
23
22
21
20
19
18
17
16
bit
D23
D22
D21
D20
D19
D18
D17
D16
0
0
0
0
0
0
0
0
Initial value
R,W
R,W
R,W
R,W
R,W
R,W
R,W
R,W
Attribute
15
14
13
12
11
10
9
8
bit
D15
D14
D13
D12
D11
D10
D9
D8
0
0
0
0
0
0
0
0
Initial value
R,W
R,W
R,W
R,W
R,W
R,W
R,W
R,W
Attribute
7
6
5
4
3
2
1
0
bit
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
0
0
0
0
Initial value
R,W
R,W
R,W
R,W
R,W
R,W
R,W
R,W
Attribute
The receive data register (RDR) is a 32-bit data buffer register for serial data reception.
⋅
Serial data signals sent to the serial input pin (SIN pin) are converted in the shift register and stored in
the receive data register (RDR).
Depending on the data length, received data will be filled from the lower bit and other bits become "0".
Example: When the data length is 8 bits and "45"h is received: D7-D0="45"h, D31-D8=0
⋅
When the received data is stored in the receive data register (RDR), the reception data full flag bit
(SSR:RDRF) will be set to "1". When reception interrupts are enabled (SSR:RIE=1), a reception
interrupt request will be generated.
⋅
The receive data register (RDR) should be read out when the reception data full flag bit (SSR:RDRF) is
"1". The reception data full flag bit (SSR:RDRF) will be automatically cleared to "0" when the receive
data register (RDR) has been read out.
⋅
In case a reception error occurs (SSR:ORE is "1"), data in the receive data register (RDR) will become
invalid.
⋅
When you read RDR, accesses must be made with following methods.
⋅
SSR:AWC=0: 16-bit access to lower 16 bits of RDR
⋅
SSR:AWC=1: 32-bit access
⋅
SSR:AWC=1 allows one-time read for any data length.
⋅
SSR:AWC=0 allows one-time read for any data length from 5 to 16 bits.
⋅
SSR:AWC=0 allows two-time reads for any data length with 20, 24, 32 bits.
When you select one of lower bits (SSR:ES=0), first read must be lower 16 bits of received data and
Fsecond read must be upper 16 bits of received data.
MB91520 Series
MN705-00010-1v0-E
1367