Use atomic wait/notify on RXTAIL in KEY

This enables waiting on them with memory.atomic.wait32 (there is no
wait8) which is needed to avoid spinning when waiting for a key.

README.md

@@ -44,12 +44,12 @@ You could use any HTTP server that sets these headers.
 
 | Name   | Address | Size / B | Access       |
 |--------|---------|----------|--------------|
-| TXBUF  | 0       | 32       | write        |
-| RXBUF  | 32      | 32       | read         |
-| TXHEAD | 64      | 1        | atomic read  |
-| TXTAIL | 65      | 1        | atomic write |
-| RXHEAD | 66      | 1        | atomic write |
-| RXTAIL | 67      | 1        | atomic read  |
+| TXBUF  | 00h     | 32       | write        |
+| RXBUF  | 20h     | 32       | read         |
+| TXHEAD | 40h     | 4        | atomic read  |
+| TXTAIL | 44h     | 4        | atomic write |
+| RXHEAD | 48h     | 4        | atomic write |
+| RXTAIL | 4Ch     | 4        | atomic read  |
 
 For both sending (`TX`) and receiving (`RX`), there are three
 registers: `xBUF`, `xHEAD` and `xTAIL`:
@@ -67,7 +67,7 @@ unoccupied byte between the tail and the head.
 
 | Name     | Address | Size / B | Access       |
 |----------|---------|----------|--------------|
-| SYSREADY | 68      | 1        | atomic write |
+| SYSREADY | 50h     | 1        | atomic write |
 
 The `SYSREADY` register is used to indicate when the system has booted
 up and is ready for user input.

emu.js

@@ -1,14 +1,14 @@
-const TXBUF = 0;
-const RXBUF = 32;
-const TXHEAD = 64;
-const TXTAIL = 65;
-const RXHEAD = 66;
-const RXTAIL = 67;
-const SYSREADY = 68;
+const TXBUF = 0x00;
+const RXBUF = 0x20;
+const TXHEAD = 0x40;
+const TXTAIL = 0x44;
+const RXHEAD = 0x48;
+const RXTAIL = 0x4c;
+const SYSREADY = 0x50;
 
 const TXBUF_SIZE = 32;
 const RXBUF_SIZE = 32;
-const PERIPHS_SIZE = 69; // Nice
+const PERIPHS_SIZE = 81;
 
 const POLL_INTERVAL_MS = 20;
 
@@ -27,6 +27,7 @@ class Emulator {
 		this.mem_u8 = new Uint8Array(this.mem.buffer);
 		for (let i = 0; i < PERIPHS_SIZE; ++i)
 			this.mem_u8[i] = 0;
+		this.mem_i32 = new Int32Array(this.mem.buffer);
 
 		this.decoder = new TextDecoder('utf-8');
 		this.encoder = new TextEncoder('utf-8');
@@ -103,6 +104,7 @@ class Emulator {
 			tail = this.fifo_next(tail);
 		} while (this.fifo_next(tail) != head && this.rx_queue.length != 0);
 		Atomics.store(this.mem_u8, RXTAIL, tail);
+		Atomics.notify(this.mem_i32, RXTAIL / 4);
 	}
 
 	print(str) {

prelude.f

@@ -63,18 +63,6 @@
 
 46 EMIT
 
-\ Peripheral register addresses
-
-: TXBUF 0 ;
-: RXBUF 32 ;
-: TXHEAD 64 ;
-: TXTAIL 65 ;
-: RXHEAD 66 ;
-: RXTAIL 67 ;
-: SYSREADY 68 ;
-
-46 EMIT
-
 \ Printing utilities
 
 : CR 10 EMIT ;
@@ -214,6 +202,22 @@ CHAR . EMIT
 
 CHAR . EMIT
 
+\ Peripheral register addresses
+
+HEX
+
+00 CONSTANT TXBUF
+20 CONSTANT RXBUF
+40 CONSTANT TXHEAD
+44 CONSTANT TXTAIL
+48 CONSTANT RXHEAD
+4C CONSTANT RXTAIL
+50 CONSTANT SYSREADY
+
+DECIMAL
+
+46 EMIT
+
 \ A better word-not-found handler
 
 : ANY-RX? RXHEAD AC@ RXTAIL AC@ <> ;

wipforth.wat

@@ -8,9 +8,9 @@
  (global $TXBUF  i32 (i32.const 0x0000))
  (global $RXBUF  i32 (i32.const 0x0020))
  (global $TXHEAD i32 (i32.const 0x0040))
- (global $TXTAIL i32 (i32.const 0x0041))
- (global $RXHEAD i32 (i32.const 0x0042))
- (global $RXTAIL i32 (i32.const 0x0043))
+ (global $TXTAIL i32 (i32.const 0x0044))
+ (global $RXHEAD i32 (i32.const 0x0048))
+ (global $RXTAIL i32 (i32.const 0x004c))
 
  ;; Forth registers
  (global $rsp (mut i32) (i32.const 0))
@@ -628,15 +628,24 @@
  ;; Serial I/O
 
  (func $key (local $head i32)
-       ;; Wait for RXBUF to be non-empty
-       loop $wait
        global.get $RXHEAD
        i32.atomic.load8_u
        local.tee $head
+
+       ;; Wait for RXBUF to be non-empty
+       loop $wait (param i32)
          global.get $RXTAIL
          i32.atomic.load8_u
          i32.eq
-         br_if $wait
+		 if
+		   global.get $RXTAIL
+		   local.get $head
+		   i64.const -1
+		   memory.atomic.wait32
+
+		   local.get $head
+		   br $wait
+		 end
        end
 
        ;; Read byte at head position
@@ -1395,7 +1404,7 @@
  ;;
  ;;   DUP DUP 65 >= SWAP 90 <= AND  \ Test if A-Z
  ;;   0BRANCH [60]                  \ Jump to invalid digit if not
- ;;   45 -                          \ Get digit value
+ ;;   55 -                          \ Get digit value
  ;;
  ;;   DUP DUP 0>= SWAP BASE @ < AND \ Test if 0 <= value < BASE
  ;;   0BRANCH [8]                   \ Jump to invalid digit if not
@@ -1438,7 +1447,7 @@
        "\b4\04\00\00"  ;; 0BRANCH
        "\3c\00\00\00"  ;; 60
        "\18\04\00\00"  ;; LIT
-       "\2d\00\00\00"  ;; 45
+       "\37\00\00\00"  ;; 55
        "\cc\02\00\00"  ;; -
        "\08\02\00\00"  ;; DUP
        "\08\02\00\00"  ;; DUP