m5m51016btp Renesas Electronics Corporation., m5m51016btp Datasheet - Page 293

• Manufacturer Part Number: m5m51016btp
• Description: Renesas 16-bit Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

M30245 Group
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
2.17 Programmable I/O Ports Usage
2.17.1 Overview of the programmable I/O ports usage
Eighty-one programmable I/O ports and one input-only port are available. I/O pins also serve as I/O pins
for built-in peripheral functions.
Each port has a direction register that defines the I/O direction and also has a port register for I/O data. In
addition, each port has a pull-up control register that defines pull-up in terms of 4 bits. The input-only port
has neither direction register nor pull-up control bit.
The following is an overview of the programmable I/O ports usage:
(1) Writing to a port register
(2) Reading a port register
(3) Input-only port
(4) Setting pull-up
(5) Setting drive capacity
With the direction register set to output, the level of the written values from each relevant pin is output
by writing to a port register. The output level conforms to CMOS output. Port P7
channel open drain. Writing to the port register, with the direction register set to input, inputs a value
to the port register, but nothing is output to the relevant pins. The output level remains floating.
In memory expansion and microprocessor mode, the contents of corresponding port and direction
registers of pins A0 to A19, D0 to D15, CS0 to CS3, RD, WRL/WR, WRH/BHE, ALE, RDY, HOLD,
HLDA and BCLK cannot be modified.
With the direction register set to output, reading a port register takes out the content of the port regis-
ter, not the content of the pin. With the direction register set to input, reading the port register takes out
the content of the pin.
P8
be set to this port. As NMI cannot be disabled, an NMI interrupt occurs if a falling edge is input to P8
Use P8
The pull-up control bit allows setting of the pull-up, in terms of 4 bits, either in use or not in use. For the
four bits chosen, pull-up is effective only in the ports whose direction register is set to input. Pull-up is
not effective in ports whose direction register is set to output.
Do not set pull-up of corresponding pin when X
Pull-up can be set for P0 to P3, P4
for P0 to P3, P4
of register can be changed, but the pull-up resistance is not connected.
A normal drive and N-channel high drive for the N-channel transistor drive capacity of port P7 can be
selected. Port P7 can be configured to drive an LED by increasing the drive strength of the corre-
sponding N-channel transistor bits.
_________
5
is used as the input-only port, it also serves as NMI. P8
5
for reading the level input at this time only.
page 284 of 354
0
to P4
_______
3
, P5
0
to P5
0
3
to P4
in memory expansion and microprocessor modes. The contents
_______
3
, P5
0
CIN
to P5
_______
_______
/X
_______
COUT
3
_____
in only single-chip mode. Pull-up cannot be set
is set or a port is used as A/D input.
________ ______
5
has no direction register. Pull-up cannot
________ _______
2. Programmable I/O Ports
0
and P7
_______
1
__________
are N
5
.