Here is a list of the port addresses used with their decoding. For the reason mentioned, only the ULA has an even port address and every even-numbered port **IN** will result in the ULA being read. | R | W | A15 | A14 | A13 | A12 | A11 | A10 | A9 | A8 | A7 | A6 | A5 | A4 | A3 | A2 | A1 | A0 | Port (Hex) | Description | |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | FEh | ULA | | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | FFh | Timex video, Floating bus | | | ■ | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 7FFDh | Memory Paging Control | | | ■ | 0 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 7FFDh | Memory Paging Control (+3/Next only) | | | ■ | 1 | 1 | 0 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | DFFDh | Next Memory Bank Select[^p230-1] | | | ■ | 0 | 0 | 0 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 1FFDh | +3 Memory Paging Control | | ■ | | 0 | 0 | 1 | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 2FFDh | +3 FDC Status | | ■ | ■ | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 3FFDh | +3 FDC Control | | | ■ | 1 | 1 | 1 | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | EFF7h | Pentagon 1024K Memory Paging Cntl. | | ■ | | 0 | 0 | 0 | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | | +3 Floating bus | | ■ | ■ | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 243Bh | NextREG Select | | ■ | ■ | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 253Bh | NextREG Data | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 103Bh | I²C SCL | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 113Bh | I²C SDA | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 123Bh | Layer 2 | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 133Bh | UART Tx | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 143Bh | UART Rx | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 153Bh | UART Select | | ■ | ■ | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 163Bh | UART Frame | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 183Bh | CTC Channel 0[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 193Bh | CTC Channel 1[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1A3Bh | CTC Channel 2[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1B3Bh | CTC Channel 3[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | [colour: light orange] 1C3Bh | [colour: light orange] CTC Channel 4[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | [colour: light red] 1D3Bh | [colour: light red] CTC Channel 5[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | [colour: light orange] 1E3Bh | [colour: light orange] CTC Channel 6[^p230-2] | | ■ | ■ | 0 | 0 | 0 | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | [colour: light red] 1F3Bh | [colour: light red] CTC Channel 7[^p230-2] | | | ■ | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | BF3Bh | ULAplus Register | | ■ | ■ | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | FF3Bh | ULAplus Data | | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0Bh | z80DMA[^p230-3] | | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 6Bh | zxnDMA[^p230-3] | | ■ | ■ | 1 | 1 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 0 | 1 | FFFDh | AY Register | | ■ | ■ | 1 | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 0 | 1 | BFFDh | AY Data (readable on +3/Next only) | | ■ | | 1 | 0 | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 0 | 1 | BFF5h | AY Inf (inside BFFDh decoding) | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1Fh | DAC A | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | F1h | DAC A[^p230-4] | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 3Fh | DAC A | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 0Fh | DAC B | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | F3h | DAC B | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | DFh | DAC A,D | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | FBh | DAC A,D | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | B3h | DAC B,C | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 4Fh | DAC C | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | F9h | DAC C[^p230-4] | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 5Fh | DAC D | | | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | E7h | SPI CS (SD card, Flash, RPi0) | | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | EBh | SPI DATA | | ■ | ■ | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | [colour: pale pink] | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | E3h | divMMC control | [^p230-1]: *Precedence over AY* [^p230-2]: *Temporarily reduced to first four CTC channels only* [^p230-3]: *Selecting either DMA port, also selects the mode in which the DMA operates* [^p230-4]: *Precedence over xxFD*