II CORE BLOCK: BCU (Bus Control Unit)
B-II-4-16 EPSON S1C33L03 FUNCTION PART
Data retained
15
Data bus
0#WRL
0
0
#WRH
X
X
A0
0
1
A1
∗
∗
No.
1
2
Byte 0
Data retained Byte 1
Byte 3 Byte 2 Byte 1 Byte 0
31 0
A[1:0]=∗0A[1:0]=∗1
0
1
880
Source (general-purpose register)
Destination (8-bit device)
2
Bus operation
(X: Not connected/Unused)
Little-endian
Byte 1
15
Data bus
0#WRL
0
0
#WRH
0
0
A0
0
1
A1
∗
∗
No.
1
2
Data retained
Byte 0 Data retained
Byte 3 Byte 2 Byte 1 Byte 0
31 0
A[1:0]=∗1A[1:0]=∗0
0
2
880
Source (general-purpose register)
Destination (8-bit device)
1
Bus operation
(∗: Uniformly 1 or 0)
Big-endian
Figure 4.13 Half-word Data Writing to an 8-bit Device
Ignored
15
Data bus
0#WRL
1
1
#WRH
X
X
A0
0
1
A1
∗
∗
No.
1
2
Byte 0
Ignored Byte 1
Byte 1 Byte 0
31 0
A[1:0]=∗0A[1:0]=∗1
0
1
880
2
Bus operation
(X: Not connected/Unused)
Destination (general-purpose register)
Source (8-bit device)
Sign or Zero extension
Little-endian
Byte 1
15
Data bus
0#WRL
1
1
#WRH
1
1
A0
0
1
A1
∗
∗
No.
1
2
Ignored
Byte 0 Ignored
Byte 1 Byte 0
31 0
A[1:0]=∗1A[1:0]=∗0
0
2
880
1
Bus operation
Destination (general-purpose register)
Sign or Zero extension
Big-endian
(∗: Uniformly 1 or 0)
Figure 4.14 Half-word Data Reading from an 8-bit Device
Data retained
15
Data bus
0#WRL
0
#WRH
X
A0
∗
A1
∗
No.
1 Byte 0
Byte 3 Byte 2 Byte 1 Byte 0
31 0
A[1:0]=
∗∗
0
1
8
Source (general-purpose register)
Destination (8-bit device)
Bus operation
(X: Not connected/Unused)
Little-endian
Byte 0
15
Data bus
0#WRL
1
#WRH
0
A0
∗
A1
∗
No.
1 Data retained
Byte 3 Byte 2 Byte 1 Byte 0
31 0
A[1:0]=
∗∗
0
1
8
Source (general-purpose register)
Destination (8-bit device)
Bus operation
Big-endian
Figure 4.15 Byte Data Writing to an 8-bit Device
Ignored
15
Data bus
0#WRL
1
#WRH
X
A0
∗
A1
∗
No.
1 Byte 0
Byte 0
31 0
A[1:0]=∗∗
0
1
8
Bus operation
(X: Not connected/Unused)
Destination (general-purpose register)
Source (8-bit device)
Sign or Zero extension
Little-endian
Byte 0
15
Data bus
0#WRL
1
#WRH
1
A0
∗
A1
∗
No.
1 Ignored
Byte 0
31 0
A[1:0]=∗∗
0
1
8
Bus operation
Destination (general-purpose register)
Source (8-bit device)
Sign or Zero extension
Big-endian
Figure 4.16 Byte Data Reading from an 8-bit Device