Can the device do it? bdnvl and bdnvs

Yesterday you asked whether a device is there. Today you ask whether it can do something. A gas sensor has no switch, a wall heater no thermometer. If you read Temperature from a heater, the chip reports IncorrectLogicType and stays on that line.

When that happens#

As long as you know every device, the error hardly ever occurs. It shows up when the chip does not know what sits on a pin:

• a universal chip you attach to different devices
• a loop over all pins with dr0
• a ReferenceId someone else entered

bdnvl: can it read that?#

bdnvl device Temperature no_thermo     # jumps if not readable
l temp device Temperature

bdnvl stands for branch if device not valid for load: the chip jumps if the device can not read this LogicType. Otherwise it continues on the next line, and reading is safe.

bdnvs: can it write that?#

bdnvs device On not_switchable         # jumps if not writable
s device On 1

bdnvs (not valid for store) checks writing. A gas sensor cannot write On, a wall heater can.

Both take a device like l and s: a pin, db or a register with a ReferenceId. There is no counterpart for lbn. There the chip checks all matching devices before reading and reports IncorrectLogicType as soon as one of them lacks the value.