CONNECTION WITH EXTERNAL DEVICES
7902 Group User’s Manual
3-2
3.1 Signals required for accessing external devices
This chapter explains the functions for connection with external devices.
The bus interface unit (BIU) controls the following. (Refer to section “2.2 Bus interface unit (BIU).”:
Reading data from devices connected externally
Writing data to devices connected externally
The bus cycle at access to external devices can be changed by the chip select wait controller (CSWC) and
Ready function. Also, by Hold function, buses can be opened to the external.
3.1 Signals required for accessing external devices
When connecting devices externally, make sure that the microcomputer operates in the memory expansion
or microprocessor mode. (Refer to section “2.5 Processor modes.”) While the microcomputer operates in
one of these modes, a part of programmable I/O port pins serve as I/O pins of signals required for accessing
external devices.
Figure 3.1.1 shows the pin configuration in the memory expansion and microprocessor modes, Figure 3.1.2
shows the external area, Table 3.1.1 lists the pins used for accessing external devices.
Fig. 3.1.1 Pin configuration in memory expansion and microprocessor modes (Top view)
Outline: 100P6Q-A
When BYTE = VCC,
P20 to P27
When BYTE = VSS,
D8 to D15
When BYTE = VCC,
P3
When BYTE = VSS,
BHW
P4
1
/φ
1
P4
0
/ALE
P4
2
/HLDA
P4
5
/CS
1
P6
0
/TA4
OUT
P6
1
/TA4
IN
P6
2
/INT
0
P6
3
/INT
1
P6
4
/INT
2
P6
5
/TB0
IN
P6
6
/TB1
IN
P5
0
/TA0
OUT
/RTP0
0
P5
1
/TA0
IN
/RTP0
1
P5
2
/TA1
OUT
/RTP0
2
P5
3
/TA1
IN
/RTP0
3
P5
4
/TA2
OUT
/RTP1
0
/KI
0
P5
5
/TA2
IN
/RTP1
1
/KI
1
P5
6
/TA3
OUT
/RTP1
2
/KI
2
P5
7
/TA3
IN
/RTP1
3
/KI
3
P4
6
/CS
2
P4
4
/CS
0
P4
3
/HOLD
P4
7
/CS
3
P6
7
/TB2
IN
P7
0
/AN
0
100
9
8
9
7
9
6
59
58
57
56
55
54
53
52
51
95
74
73
72
71
70
69
68
67
66
64
63
62
61
60
65
75
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
30
29
28
27
26
40
37
36
38
35
34
33
32
31
39
50
49
48
47
46
45
44
43
42
41
25
24
23
22
21
3
2
1
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
VCC
VSS
XOUT
XIN
VCONT
RESET
MD0
D3/LA3
D4/LA4
D5/LA5
P25/D13
P24/D12
P23/D11
P20/D8
D7/LA7
P22/D10
P21/D9
D6/LA6
P27/D15
P26/D14
P33/BHW
RD
BLW
P30/RDY
BYTE
V
SS
MD1
A
4
A
5
A
6
A
7
P11
0
/A
8
P11
1
/A
9
P11
2
/A
10
P11
3
/A
11
P11
4
/A
12
P11
5
/A
13
P11
6
/A
14
P11
7
/A
15
P0
0
/A
16
P0
1
/A
17
P0
2
/A
18
P0
3
/A
19
P0
4
/A
20
P0
5
/A
21
P0
7
/A
23
P0
6
/A
22
D
0
/LA
0
D
1
/LA
1
D
2
/LA
2
A3
A1
A2
P87/TXD1
A0
P81/CTS0/CLK0
P82/RXD0
P83/TXD0
VSS
AVSS
VREF
VCC
AVCC
P73/AN3
P72/AN2
P71/AN1
P84/CTS1/RTS1/INT4
P85/CTS1/CLK1
P86/RXD1
P74/AN4/(INT3)
P75/AN5/(INT4)
P76/AN6/DA0
P77/AN7/ADTRG/DA1/(INT2)
P80/CTS0/RTS0/DA2/INT3
NMI