Diamond Systems Hercules III, User Manual, Page: 77 / 86

Hercules III User Manual Rev A.2
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77
19. DIGITAL I/O OPERATION
Hercules III contains 40 digital I/O lines organized as five 8-bit I/O ports: Port A-E. The direction of each port is
programmable. Port E is also used for the PWM outputs. The port data are accessed at registers Base+16
through Base+20, and the port direction register is located at Base+22.
Base + 7 6 5 4 3 2 1 0
16 DIOA7 DIOA6 DIOA5 DIOA4 DIOA3 DIOA2 DIOA1 DIOA0
17 DIOB7 DIOB6 DIOB5 DIOB4 DIOB3 DIOB2 DIOB1 DIOB0
18 DIOC7 DIO6 DIOC5 DIOC4 DIOC3 DIOC2 DIOC1 DIOC0
19 DIOD7 DIOD6 DIOD5 DIOD4 DIOD3 DIOD2 DIOD1 DIOD0
20 DIOE7 DIOE6 DIOE5 DIOE4 DIOE3 DIOE2 DIOE1 DIOE0
21 - - - - - - - -
22 MODE P2 P1 PO/DIRE B2/DIRD B1/DIRC B0/DIRB D/DIRA
The digital I/O lines are located on I/O header J8. The lines are 3.3V and 5V logic compatible. Each output is
capable of supplying
–8mA in logic 1 state and +12mA in logic 0 state.
DIRA, DIRB, DIRC, DIRD, and DIRE control the direction of ports A, B, C, D and E respectively. A direction value
of 0 means output and 1 means input. All ports power up to input mode and the output registers are cleared to
zero. When a port direction is changed to output, its output register is cleared to zero. When a port is in output
mode, its value can be read back.