84PCE:Ports:5000
From WikiTI
This port range has an interesting semi-pattern of read-only and latching ports. Some of these ports have a critical function for interrupt-handling. A partial list is below, but ports with some kind of function continue until at least 5055.
This range is (probably?) memory-mapped to F00000.
| Port | Default | Bits | Information |
| 5000 | 00 | ?? | May or may not serve a purpose? |
| 5001 | 80 | ?? | Bit 2 is set while any key is being pressed |
| 5002 | 00 | ?? | Ports 5002-5003 may always read zero |
| 5004 | 11 | FF | Reset bit 4 to freeze |
| 5005 | 30 | FF | Setting bit 2 or bit 7 (or both) will freeze the calculator |
| 5006 | 00 | 3F | Latches value written |
| 5007 | 00 | Ports 5007-500B may always read zero | |
| 500C | 19 | FF | Reset bit 4 to freeze |
| 500D | 00 | FF | Latches value written |
| 500E | 00 | 3F | Latches value written |
| 500F | 00 | Port 500F may always read zero | |
| 5010 | 00 | FF | Latches value written |
| 5011 | 00 | FF | Latches value written |
| 5012 | 00 | 3F | Latches value written |
| 5013 | 00 | ?? | Ports 5013-5020 may always read zero |
| 5015 | 00 | ?? | Read by the boot code at 001327h after power-off? |
| 5021 | 90 | ?? | Bit 3 is set when a key is held |
| 5022 | 08 | ?? | Writes do not change value |
| 5023 | 00 | ?? | Port 5023 may always read zero |
| 5024 | 00 | FF | Latches value written |
| 5025 | 00 | FF | Latches value written |
| 5026 | 00 | 3F | Latches value written |
| 5027 | 00 | ?? | Ports 5027-502B may always read zero |
| 502C | 00 | FF | Latches value written |
| 502D | 00 | FF | Latches value written |
| 502E | 00 | 3F | Latches value written |
