Interrupt on keypress mode

2026-08-17 16:02:44 -04:00
parent 91c9d49d1b
commit 08624925fe
11 changed files with 365 additions and 18 deletions
@@ -0,0 +1,161 @@
+; Tests interrupt on input: the console asking for attention instead of being asked.
+;
+; The control port has two bits and they are independent of one another. Bit 0 puts the
+; console in key mode; bit 1 says to put the interrupt line up when a byte arrives. The
+; console is on port 0x00, so that is the vector a key comes through - a device raises its
+; line on its base port, and the status and control ports belong to the same device as the
+; data port.
+;
+; The main program does nothing at all but wait to be told it is finished. It never looks
+; at the console, which is the whole point: every byte is dealt with by the handler.
+;
+; What the status bits mean:
+;   bit 0  READY       reading the data port will not have to wait
+;   bit 1  ENDED       input has run out for good
+;   bit 2  KEYMODE     the console is in key mode
+;   bit 3  INTERRUPTS  the console is set to raise its line when a byte arrives
+;
+; This runs with input from a file rather than a terminal, so key mode has no terminal to
+; put into another state and nothing here depends on one. A pipe with bytes in it is a
+; console with keys waiting as far as the console is concerned.
+
+#Include console.asm
+
+#Program
+
+start:
+  CIF                       ; Nothing gets through until there is something to catch it.
+
+  SETD.0 Banner
+  CALL printString
+  CALL newLine
+
+  ; Key mode and interrupt on input, asked for in one write. Neither bit depends on the
+  ; other, so there is no order to get wrong.
+  INIA 0x03
+  OUTA 0x02
+  SETD.0 AskedLabel
+  CALL printString
+  CALL showStatus
+
+  SETD.0 ArrivedLabel
+  CALL printString
+  CALL newLine
+
+  SIF                       ; From here a byte arriving runs keyHandler.
+
+waitLoop:
+  ; Waiting without looking. Nothing in this loop touches the console, so every byte that
+  ; comes out below was put there by something that interrupted this.
+  SETD.3 Finished
+  LDA.3
+  RSTB
+  OR                        ; Q is the flag, so this is a test for zero.
+  BRQ waitLoop
+
+  CALL newLine
+  RSTA
+  OUTA 0x02                 ; Line mode and no interrupts, the way it was found.
+  SETD.0 DoneLabel
+  CALL printString
+  CALL showStatus
+  HALT
+
+; Entered because the console had something to say. It is never called.
+;
+; DP3 is used freely here: an interrupt saves all four Data Pointers and RETI puts them
+; back, so a handler cannot disturb what it interrupted no matter what it touches.
+keyHandler:
+  INA 0x01
+  INIB 0x02                 ; ENDED
+  AND
+  BNQ keyEnded
+  INA 0x00                  ; The byte this interrupt was about.
+  OUTA 0x00                 ; Nothing echoes in key mode, so the program does it.
+  RETI
+
+keyEnded:
+  ; The end of input raises the line once, so a program driven entirely by interrupts
+  ; still finds out that nothing more is coming. Without it this would wait forever for a
+  ; key that cannot arrive.
+  SETD.3 Finished
+  INIA 0x01
+  STA.3
+  RETI
+
+; Prints the status byte as hex and then names the bits that are up, so a change in the
+; output says which bit moved rather than only that the number is different.
+showStatus:
+  INA 0x01
+  PSHA
+  CALL printByteHex
+  INIA 0x20
+  OUTA 0x00
+  POPA
+  PSHA
+
+  INIB 0x01
+  AND
+  BRQ showNotReady
+  SETD.0 ReadyWord
+  CALL printString
+showNotReady:
+  POPA
+  PSHA
+
+  INIB 0x02
+  AND
+  BRQ showNotEnded
+  SETD.0 EndedWord
+  CALL printString
+showNotEnded:
+  POPA
+  PSHA
+
+  INIB 0x04
+  AND
+  BRQ showNotKeys
+  SETD.0 KeysWord
+  CALL printString
+showNotKeys:
+  POPA
+
+  INIB 0x08
+  AND
+  BRQ showNotInterrupts
+  SETD.0 InterruptsWord
+  CALL printString
+showNotInterrupts:
+  CALL newLine
+  RET
+
+#Data
+
+Banner:
+"console input interrupts"
+
+AskedLabel:
+"asked for:  "
+ArrivedLabel:
+"what arrived:"
+DoneLabel:
+"at the end: "
+
+ReadyWord:
+"ready "
+EndedWord:
+"ended "
+KeysWord:
+"keys "
+InterruptsWord:
+"interrupts "
+
+; Set by the handler when the console says there will be no more bytes. It is the only
+; thing the handler and the program it interrupts have to say to each other.
+Finished:
+  0x00
+
+#Vectors
+
+  Boot         start
+  Device 0x00  keyHandler
@@ -10,6 +10,10 @@
 ;   bit 1  ENDED    input has run out for good
 ;   bit 2  KEYMODE  the console is in key mode
 ;
+; There is a fourth bit, for whether the console interrupts on input, and nothing here
+; sets it. Polling and interrupting are the two ways to get a byte and this is the one
+; about polling; consoleInterruptTest.asm is the other.
+;
 ; This runs with input from a file rather than a terminal, so key mode has no terminal to
 ; put into another state and the mode bit is the only thing that changes. That is on
 ; purpose: the same program has to work either way, and a test that needed a terminal
@@ -60,8 +64,9 @@ readDone:

  ; ---- The status at the end of input ----
  ;
-  ; READY is set as well as ENDED, because a read does answer at once. It just answers
-  ; 0xFF forever. ENDED is what says so.
+  ; ENDED is set and READY is clear, although a read would answer at once here: what it
+  ; answers is 0xFF standing in for nothing. READY means there is a byte to be had, so the
+  ; loop above stops on its own rather than taking imaginary bytes forever.
  SETD.0 AtEndLabel
  CALL printString
  CALL showStatus