Difference between revisions of "86:Ports:03"
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=== Read Values === | === Read Values === | ||
* Bit 0: Set if the ON key generated an interrupt. | * Bit 0: Set if the ON key generated an interrupt. | ||
| − | * Bit 1: Set if the LCD controller generated an interrupt (after DMA for rows 17 & 49). Used by the OS as a periodic interrupt source (approximately 200 Hz). | + | * Bit 1: Set if the [[86:LCD_Controller|LCD controller]] generated an interrupt (after [[86:LCD_Controller#DMA|DMA]] for rows 17 & 49). Used by the OS as a periodic interrupt source (approximately 200 Hz). |
* Bit 2: Set if the /INT pin generated an interrupt (unused on the TI-86). | * Bit 2: Set if the /INT pin generated an interrupt (unused on the TI-86). | ||
* Bit 3: Reset if the ON key is being pressed; set otherwise. | * Bit 3: Reset if the ON key is being pressed; set otherwise. | ||
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=== Write Values === | === Write Values === | ||
* Bit 0: Set 0 to disable ON key interrupts and to acknowledge an ON key interrupt. Set 1 to enable ON key interrupts. | * Bit 0: Set 0 to disable ON key interrupts and to acknowledge an ON key interrupt. Set 1 to enable ON key interrupts. | ||
| − | * Bit 1: Set 0 to disable LCD controller interrupts & to acknowledge an interrupt from the LCD controller. Set 1 to enable interrupts from the | + | * Bit 1: Set 0 to disable [[86:LCD_Controller#Interrupts|LCD controller interrupts]] & to acknowledge an interrupt from the LCD controller. Set 1 to enable interrupts from the LCD controller. |
* Bit 2: Set 0 to disable external interrupts & to acknowledge an external interrupt. Set 1 to enable external interrupts. | * Bit 2: Set 0 to disable external interrupts & to acknowledge an external interrupt. Set 1 to enable external interrupts. | ||
| − | * Bit 3: Set 0 to turn off the LCD. Set 1 to turn on the LCD. | + | * Bit 3: Set 0 to turn off the LCD. Set 1 to turn on the LCD. When the LCD is off, DMA & LCD interrupts do not occur. |
* Bit 4-7: Unused. | * Bit 4-7: Unused. | ||
Latest revision as of 06:03, 20 September 2021
Synopsis
Port Number: 03h
Function: Interrupt Control Port
This port controls all devices that can generate interrupts.
Read Values
- Bit 0: Set if the ON key generated an interrupt.
- Bit 1: Set if the LCD controller generated an interrupt (after DMA for rows 17 & 49). Used by the OS as a periodic interrupt source (approximately 200 Hz).
- Bit 2: Set if the /INT pin generated an interrupt (unused on the TI-86).
- Bit 3: Reset if the ON key is being pressed; set otherwise.
- Bit 4-7: Unused.
Write Values
- Bit 0: Set 0 to disable ON key interrupts and to acknowledge an ON key interrupt. Set 1 to enable ON key interrupts.
- Bit 1: Set 0 to disable LCD controller interrupts & to acknowledge an interrupt from the LCD controller. Set 1 to enable interrupts from the LCD controller.
- Bit 2: Set 0 to disable external interrupts & to acknowledge an external interrupt. Set 1 to enable external interrupts.
- Bit 3: Set 0 to turn off the LCD. Set 1 to turn on the LCD. When the LCD is off, DMA & LCD interrupts do not occur.
- Bit 4-7: Unused.
Comments
- You need to acknowledge interrupts. Otherwise a new interrupt will be generated directly after you enable interrupts again with EI. Because that disables that particular interrupt at the same time, you may have to write a second value to this port to re-enable it.
- The OS shuts down by turning off the LCD & HALTing with the ON key interrupt enabled.
