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7703 GROUP
7702/7703 Group User’s Manual
20–6
20.4 Functional description
20.4.1 I/O pin
The M37703 does not have the following pins of the M37702:
Port P33
Ports P43 to P46
Ports P60, P61, P66, P67
Ports P73 to P76
Ports P84, P85
(1) Port direction register
Fix the bits of port Pi (i = 3, 4, 6, 7, 8) direction register which do not have the corresponding pins
to “1.” All products of the M37703 need this procedure. Do it regardless of the product type and the
used mode.
All bits of port Pi direction register are cleared to “0” after reset. Accordingly, follow the procedure
shown by Figure 20.4.1 in the initial setting program after reset. Do not write “0” after that to the bits
to be fixed to “1.”
Paragraph “1.3.1 Example for processing unused pins” explains the examples when there are pins,
however, those pins are not used. The above explanation is independent of that example explanation.
(2) Memory expansion and Microprocessor modes
_____
The M37703 does not have the HLDA pin, so that the HLDA signal cannot be used in those modes.
b1
b0
b2
b3
b4
b5
b6
b7
1
111 1
11
111 1
11
qBe sure to set “1” to the bit indicated by using “1”.
Though these bits do not have the corresponding pins, follow the above procedure.
The above procedure is necessary whether or not other programmable I/O ports are
used.
Port P3 direction register (address 916)
Port P4 direction register (address C16)
Port P6 direction register (address 1016)
Port P7 direction register (address 1116)
Port P8 direction register (address 1416)
Notes 1: When executing the instruction to write to bits 4 to 7 of Port P3 direction register, the value cannot be
written into them.
When reading to those bits, “0” is read.
2: The bits which are not indicated by using “1” and bits 4 to 7 of Port P3 direction register function as a
programmable I/O port. Just as in ports P0–P2 and P5, set “0” when using as an input port, and set “1”
when using as an output port.
Fig. 20.4.1 Procedure of port Pi (i = 3, 4, 6, 7, 8) direction register