83Plus:Ports:03

Synopsis

Port Number: 03h

Function: Interrupt Masking Port

This port controls what devices will be allowed to trigger interrupts.

Read Values

• Bit 0: Set if pressing the ON key will generate an interrupt.
• Bit 1: Set if the hardware timer will generate an interrupt (~150 times per second).
• Bit 4: Set if the linkport will generate an interrupt.

Write Values

• Bit 0: Set 1 to enable the ON key. Set 0 to disable it.
• Bit 1: Set 1 to enable the hardware timer. Set 0 to disable it.
• Bit 3: Set 1 to enable the LCD. Set 0 to turn off the LCD.
• Bit 4: Set 1 to enable the linkport interrupt. Set 0 to disable it. (Does not completely disable the linkport.)

Comments

For normal operation, write 0B (00001011) to this port.

Example

This example shows how to do a soft powerdown (similar to the auto powerdown) on the calculator. This may or may not wipe the LCD screen, so you should first copy it's contents to a buffer like saveSScreen and then copy it back afterwards.

 push af
 ld a, 11h ;Enable linkport, ON key. Disable timer. Turn off LCD.
 out (3), a
 halt ;Wait for an interrupt (either ON key or insert link cable).
 ld a, 0Bh ;Enable ON key, tiemr. Disable linkport. Turn on LCD.
 out (3), a
 pop af

Credits and Contributions

Michael Vincent: For documenting here on the interrupt bits.