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 first hardware timer will generate an interrupt (range: 108Hz-512Hz).
• Bit 2: Set if the second hardware timer will generate an interrupt (range: 216Hz-1024Hz).
• 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 first hardware timer. Set 0 to disable it.
• Bit 2: Set 1 to enable the second hardware timer. Set 0 to disable it.
• Bit 3: Set 0 to put the calculator in low power mode if and only if the Z80 cpu enters the halt state (during the executing of a halt instruction). Set 1 to keep the calculator powered.
• 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.
• In low power mode it is known that at least the lcd driver enters standby mode and that the timer hardware has been disabled.

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.
           ;Set low power mode.
 out (3), a
 halt      ;Enter low power mode (disabling various devices)
           ;and wait for an interrupt (either ON key or
           ;link activity) which will enable all hardware
           ;devices again.
 ld a, 0Bh ;Enable ON key, timer. Disable linkport.
           ;Keep calculator powered.
 out (3), a
 pop af

Credits and Contributions

• Michael Vincent: For documenting here on the interrupt bits.
• James Montelongo: For documenting here on the interrupt bits.