BusAND (Bus AND)
Inputs
| Pin | Type | Description |
|---|---|---|
| A | bus8 | First input bus (8 bits) |
| B | bus8 | Second input bus — mask (8 bits) |
Outputs
| Pin | Type | Description |
|---|---|---|
| Q | bus8 | Bitwise AND: A & B |
How It Works
Each output bit is 1 only if both corresponding input bits are 1.
| A Bit | B Bit | Q Bit |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
Usage
Bit masking is the primary use case. Feed a mask on input B — only bits where the mask is 1 pass through from A to Q. Bits where the mask is 0 are forced to 0 regardless of A.
Preventing bus conflicts — this is critical in levels 22–29. When multiple devices share a bus, only one should drive it at a time. Using BusAND with the second input set to 0x00 forces the output to 0x00, effectively disconnecting the device from the bus. The AND gate acts as a tri-state buffer substitute. Paired with an address decoder, BusAND gates select which register or device writes to a shared data bus.