HD6433713 datasheet(63/324 Pages) RENESAS

63 / 324 page

As noted above, the H8/300L CPU executes bit manipulation instructions by a read-modify-write

operation on 8-bit data. Since the same address is used for the I/O port data register and reading

of pin input, a bit manipulation instruction designating a port functions as follows.

x High-voltage pin: pin other than the modified bit

• When set as an input pin (data register = 0)

First the CPU reads the pin input level (read), then it sets or resets the designated bit

(modify; other bits remain the same), and writes that value to the data register (write). If

the input level is high (read data = 1), a value of 1 is written to the data register, changing

the input pin to an output pin (high-level output). If the input level is low, no change

occurs.

• When set as an output pin (data register = 1, high-level output)

If the output level is higher than the input high level (VIH), there is no change.

If the output level is lower than the input low level (VIL), a value of 0 is written to the data

or high-impedance state.

If the output level is pulled down by the load to an intermediate level, the resulting state is

indeterminate.

y Standard-voltage pin: pin other than the modified bit

•

When set as an input pin

The CPU reads the pin input level and writes that value to the data register, which may or

may not result in a change to the data register contents.

•

When set as an output pin

The data register is read, so no change occurs.

Bit manipulation in registers containing write-only bits

Example: PWM data registers, etc.

(Note that read and write characteristics can differ from bit to bit.)

Write-only bits cannot be read. Write-only bits other than the intended bit are set to 1.

HD6433713 Datasheet(PDF) 63 Page - Renesas Technology Corp