II CORE BLOCK: BCU (Bus Control Unit)
S1C33T01 FUNCTION PART
EPSON
B-II-4-17
Ignored
15
Data bus
0
#WRL
1
#WRH
X
A0
0
1
0
1
A1
0
1
No.
1
2
3
4
Byte 0
Ignored
Byte 1
Ignored
Byte 2
Ignored
Byte 3
Byte 2
Byte 1
Byte 0
31
0
A[1:0]=10
A[1:0]=00
A[1:0]=11
A[1:0]=01
80
1
4
8
88
00
0
32
Bus operation
(X: Not connected/Unused)
Destination (general-purpose register)
Source (8-bit device)
Little-endian
Byte 3
15
Data bus
0
#WRL
1
#WRH
1
A0
0
1
0
1
A1
0
1
No.
1
2
3
4
Ignored
Byte 2
Ignored
Byte 1
Ignored
Byte 0
Ignored
Byte 3
Byte 2
Byte 1
Byte 0
31
0
A[1:0]=01
A[1:0]=11
A[1:0]=00
A[1:0]=10
80
4
1
8
88
00
0
23
Bus operation
Destination (general-purpose register)
Source (8-bit device)
Big-endian
Figure 4.14
Word Data Reading from an 8-bit Device
Data retained
15
Data bus
0
#WRL
0
#WRH
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]=
0
A[1:0]=
1
0
1
88
0
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
#WRH
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]=
1
A[1:0]=
0
2
88
0
Source (general-purpose register)
Destination (8-bit device)
1
Bus operation
(
: Uniformly 1 or 0)
Big-endian
Figure 4.15
Half-word Data Writing to an 8-bit Device
Ignored
15
Data bus
0
#WRL
1
#WRH
X
A0
0
1
A1
No.
1
2
Byte 0
Ignored
Byte 1
Byte 0
31
0
A[1:0]=
0
A[1:0]=
1
0
1
88
0
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
#WRH
1
A0
0
1
A1
No.
1
2
Ignored
Byte 0
Ignored
Byte 1
Byte 0
31
0
A[1:0]=
1
A[1:0]=
0
88
0
1
Bus operation
Destination (general-purpose register)
Source (8-bit device)
Sign or Zero extension
Big-endian
(
: Uniformly 1 or 0)
Figure 4.16
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 4.17
Byte Data Writing to an 8-bit Device