Toshiba TMP91C815F Data Book page 57

After Reset, the port pins listed below function as general-purpose I/O port pins.
Resetting sets I/O pins, which can be programmed for either input or output to be input ports pins. Setting the
port pins for internal function use must be done in software.
Note about bus release and programmable pull-up I/O port pins
When the bus is released (i.e. when BUSAK = 0), the output buffers for D0 to D15, A0 to A23, and the
control signals (RD, WR, HWR, R/W and CS0 to CS3, EA24, 25/CS2A to 2G/CSEXA) are off and are set to
High-Impedance.
However, the output of built-in programmable pull-up resistors are kept before the bus is released. These
programmable pull-up resistors can be selected ON/OFF by programmable when they are used as the input
ports.
When they are used as output ports, they cannot be turned ON/OFF in software.
Table 3.5.3 shows the pin states after the bus has been released.
Pin name
D0-D7
D8-D15(P10-P17)
A0-A15
A16-23(P20-P27)
/RD.
/WR
P52 (/HWR),
P56 (R/W),
P60 (/CS0),P61 (/CS1),
P62 (/CS2,/CS2A),
P63 (/CS3),
P64 (EA24,/CS2B),
P65 (EA25,/CS2C),
P66 (/CS2D), P67 (/CS2E),
P73 (/CS2F),
P74 (/CS2G),
P75 (/CSEXA)
Table 3.5.3 Pin states (after bus release)
The pin state (when the bus is released)
Port mode
The state is not changed.
(do not become to high impedance
(Hz).)
The state is not changed.
(do not become to high impedance
(Hz).)
The state is not changed.
(do not become to high impedance
(Hz).)
91C815-
54
Function mode
Become high-impedance(Hz).
First sets all bits to high, then sets them to
High-impedance(Hz).
First sets all bits to high, then the output buffer is
OFF. The programmable pull up resistor is ON
irrespective of the output
latch.
First sets all bits to high, then sets them to
high-impedance(Hz).
TMP91C815