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(4508,4509) When leaving unused pins open, how should the output latches be set?

Latest Updated:01/16/2006

Question:

(Pin, I/O Port)   When leaving unused pins open, how should the output latches be set? [2006/01/16]

Answer:

D0, 1, 4, 5: Any value of output format and output latch is acceptable.
D2, D3: Disable key-on wakeup. (K22, K23 = 0)
Do not set the output latch to 0 when the pull-up transistor is ON.
P00: Disable key-on wakeup. (K00 = 0)
Unselect the SIN pin. (J11 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P01: Disable key-on wakeup. (K01 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P02: Disable key-on wakeup. (K02 = 0)
Unselect the SCK pin. (J11, J10 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P03: Disable key-on wakeup. (K03 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P10: Disable key-on wakeup. (K10 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P11: Do not select CNTR1 input as the timer 1 count source. (W11, W10 ≠ 10)
Disable key-on wakeup. (K11 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P12: Do not select CNTR0 input as the timer 2 count source (W21, W20 ≠ 10)
Disable key-on wakeup. (K12 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P13: Disable INT pin input. (I13 = 0)
Disable key-on wakeup. (K13 = 0)
Do not set the output latch to 0 when the pull- up transistor is ON.
P20, P21: Disable key-on wakeup. (K20, K21 = 0)
Do not set the output latch to 0 when the pull-up transistor is ON.
P30, P31: Any value of output format and output latch is acceptable.

When the output format is Nch, the output latch is 1, and the pull-up transistor is off, the voltage level of the pin is undefined, but power supply current does not increase.
However, power supply current may increase during input instruction execution.
Therefore, do not use the above settings when there is the possibility of an input instruction targeting unused pins; for example, when there is a mixture of input and unused pins in the ports controlled by simultaneously by a single input instruction.
Furthermore, although increased current consumption due to increased power supply current is a disadvantage, the level of current will seldom be enough to damage the ports or the MCU. (#105586)

Suitable Products
4508
4509