2 registers, Page 5, I/o bank 0 i/o port offset: 00 hex – read/write – Sensoray 621 User Manual

Page 7: I/o bank 1 i/o port offset: 04 hex – read/write, I/o bank 2 i/o port offset: 08 hex – read/write, Bank 0 interrupt flags offset: 14 hex – read only, Bank 1 interrupt flags offset: 18 hex – read only, Bits marked with an * are read only, I/o channels 0-31, I/o channels 32-63