86:Ports:03 - Revision history

Zeroko: Fixed bit 1 & 3 write descriptions & linked to LCD controller page

2021-09-20T13:03:03Z

Fixed bit 1 & 3 write descriptions & linked to LCD controller page

Zeroko: Typo in category link

2021-09-20T06:24:11Z

Typo in category link

Zeroko: Based on 83Plus:Ports:03

2021-09-20T06:23:06Z

Based on 83Plus:Ports:03

New page

[[Category:86:Ports:By_Address|06 - Interrupt Control]] [[Category:86:Ports:By_Name|Interrupt Control]]
== 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 first timer.
* 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 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.

@@ Line 9: / Line 9: @@
 === 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 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 3: Reset if the ON key is being pressed; set otherwise.
@@ Line 16: / Line 16: @@
 === 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 first timer.
+* 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 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.

@@ Line 1: / Line 1: @@
-[[Category:86:Ports:By_Address|06 - Interrupt Control]] [[Category:86:Ports:By_Name|Interrupt Control]]
+[[Category:86:Ports:By_Address|03 - Interrupt Control]] [[Category:86:Ports:By_Name|Interrupt Control]]
 == Synopsis ==
 '''Port Number:''' 03h