When testing IOH and IOL, it is necessary to set VOL and VOL.
When testing VOH and VOL, it is necessary to set IOH and IOL.
VOH represents the minimum voltage value that the output pin can reach at a logic high level. ----Test under the most adverse conditions
IOH represents the maximum current that the output pin can drive at a logic high level.
VOL represents the maximum voltage value that the output pin can reach when the logic is low. ----Test under the most adverse conditions
IOL represents the maximum current that the output pin can drive at a logic low level.
IOH: Refers to the pulling current capability of the chip in a high-level state (i.e. when the output pin is logic "1"), also known as pull-up current. It reflects the maximum load capacity that the chip output can withstand in a high-level state.
IOL: Refers to the current sink capability of the chip in a low-level state (i.e. when the output pin is logic "0"), also known as pull-down current. It reflects the maximum load capacity that the chip output can drive in a low-level state.
Test steps:
IOH testing:

Setting the output pin of the chip to high level (logic "1") - This is usually achieved by setting the IO port to 1 in a segment of the pattern.
The VOH value needs to be set, usually for 1.8V GPIO, it is 0.5 * 1.8V.
Use an ammeter to measure the current of the output pin to ground, which is the IOH value. IOH is a negative value. Because it flows from DUT to PMU.
IOL testing:

Setting the output pin of the chip to a low level (logic "0") - This is usually achieved by setting the IO port to 1 in a segment of the pattern.
The value of VOL needs to be set, generally 1.8V GPIO is 0.5 * 1.8V.
Measure the current of the output pin to ground using an ammeter, which is the IOL value. By adjusting the load resistance, IOL values can be measured under different load conditions. IOL is a positive value. Because it flows from PMU to DUT.

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