Support keyboard transmit (bell) requests

Bumping version to 0.4.0, because this is a breaking change.

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "dmd_core"
 description = "AT&T / Teletype DMD 5620 Terminal Emulator - Core Library"
-version = "0.3.1"
+version = "0.4.0"
 authors = ["Seth Morabito <web@loomcom.com>"]
 homepage = "https://github.com/sethm/dmd_core"
 repository = "https://github.com/sethm/dmd_core"
@@ -16,4 +16,4 @@ lazy_static = "^1.2.0"
 [badges]
 travis-ci = { repository = "https://github.com/sethm/dmd_core", branch = "master" }
 
-maintenance = { status = "actively-developed" }
+maintenance = { status = "actively-developed" }

README.md

@@ -27,6 +27,10 @@ however.
 
 ## Changelog
 
+0.4.0: Breaking change. TX to the keyboard from the terminal is
+       now supported, so that clients can use it to detect when
+       a bell (^G) request has been sent.
+
 0.3.1: Added exception handling for memory errors, and a `run` function
        to free-run the CPU for a given number of steps.
 

src/bus.rs

@@ -184,8 +184,12 @@ impl Bus {
         self.duart.mouse_up(button);
     }
 
-    pub fn tx_poll(&mut self) -> Option<u8> {
-        self.duart.tx_poll()
+    pub fn rs232_tx_poll(&mut self) -> Option<u8> {
+        self.duart.rs232_tx_poll()
+    }
+
+    pub fn kb_tx_poll(&mut self) -> Option<u8> {
+        self.duart.kb_tx_poll()
     }
 
     pub fn rx_char(&mut self, char: u8) {

src/cpu.rs

@@ -1315,7 +1315,7 @@ impl Cpu {
             }
             MNEGW | MNEGH | MNEGB => {
                 let a = self.read_op(bus, 0)?;
-                let result = !a + 1;
+                let result = (!a).wrapping_add(1);
                 self.write_op(bus, 1, result)?;
                 self.set_nz_flags(result, 1);
                 self.set_c_flag(false);

src/dmd.rs

@@ -107,8 +107,15 @@ impl Dmd {
     ///
     /// Poll for a character to transmit from the terminal to the host.
     ///
-    pub fn tx_poll(&mut self) -> Option<u8> {
-        self.bus.tx_poll()
+    pub fn rs232_tx_poll(&mut self) -> Option<u8> {
+        self.bus.rs232_tx_poll()
+    }
+
+    ///
+    /// Poll for a character to transmit from the terminal to the keyboard.
+    ///
+    pub fn kb_tx_poll(&mut self) -> Option<u8> {
+        self.bus.kb_tx_poll()
     }
 
     ///

src/duart.rs

@@ -81,6 +81,7 @@ const CMD_DTX: u8 = 0x08;
 //
 const ISTS_TAI: u8 = 0x01;
 const ISTS_RAI: u8 = 0x02;
+const ISTS_TBI: u8 = 0x10;
 const ISTS_RBI: u8 = 0x20;
 const ISTS_IPC: u8 = 0x80;
 
@@ -210,34 +211,49 @@ impl Duart {
         }
     }
 
-    pub fn service(&mut self) {
-        let mut ctx = &mut self.ports[PORT_0];
+    fn handle_tx(&mut self, port: usize) {
+        let mut ctx = &mut self.ports[port];
+
+        let (tx_istat, rx_istat) = match port {
+            0 => (ISTS_TAI, ISTS_RAI),
+            _ => (ISTS_TBI, ISTS_RBI),
+        };
 
-        // Deal with RS-232 Transmit
         if (ctx.conf & CNF_ETX) != 0 &&
             (ctx.stat & STS_TXR) == 0 &&
-            (ctx.stat & STS_TXE) == 0 && Instant::now() >= ctx.next_tx {
+            (ctx.stat & STS_TXE) == 0 && Instant::now() >= ctx.next_tx
+        {
             let c = ctx.tx_data;
             ctx.stat |= STS_TXR;
             ctx.stat |= STS_TXE;
-            self.istat |= ISTS_TAI;
-            self.ivec |= TX_INT;
+            self.istat |= tx_istat;
+            // Only RS232 transmit generates an interrupt.
+            if port == 0 {
+                self.ivec |= TX_INT;
+            }
             if (ctx.mode[1] >> 6) & 3 == 0x2 {
                 // Loopback Mode.
                 ctx.rx_data = c;
                 ctx.stat |= STS_RXR;
-                self.istat |= ISTS_RAI;
+                self.istat |= rx_istat;
                 self.ivec |= RX_INT;
             } else {
                 ctx.tx_queue.push_front(c);
             }
-
-            // ctx.next_tx = Instant::now() + ctx.char_delay;
         }
+    }
+
+    pub fn service(&mut self) {
+        // Deal with RS-232 Transmit
+        self.handle_tx(PORT_0);
 
         // Deal with RS-232 Receive
         self.handle_rx(PORT_0);
 
+        // Deal with Keyboard Transmit
+        // (note: This is used only for keyboard beeps!)
+        self.handle_tx(PORT_1);
+
         // Deal with Keyboard Receive
         self.handle_rx(PORT_1);
     }
@@ -259,10 +275,14 @@ impl Duart {
         !self.outprt
     }
 
-    pub fn tx_poll(&mut self) -> Option<u8> {
+    pub fn rs232_tx_poll(&mut self) -> Option<u8> {
         self.ports[PORT_0].tx_queue.pop_back()
     }
 
+    pub fn kb_tx_poll(&mut self) -> Option<u8> {
+        self.ports[PORT_1].tx_queue.pop_back()
+    }
+
     pub fn mouse_down(&mut self, button: u8) {
         self.ipcr = 0;
         self.inprt |= 0xb;
@@ -491,8 +511,8 @@ impl Device for Duart {
                 // transmit will happen in the 'service' function.
                 ctx.next_tx = Instant::now() + ctx.char_delay;
                 ctx.stat &= !(STS_TXE | STS_TXR);
-                self.ivec &= !TX_INT;
                 self.istat &= !ISTS_TAI;
+                self.ivec &= !TX_INT;
             }
             IPCR_ACR => {
                 self.acr = val;
@@ -509,11 +529,21 @@ impl Device for Duart {
                 self.handle_command(val, PORT_1);
             }
             THRB => {
+                // TODO: When OP3 is low, do not send data to
+                // the keyboard! It's meant for the printer.
+
+                // Keyboard transmit requires special handling,
+                // because the only things the terminal transmits to
+                // the keyboard are status requests, or keyboard beep
+                // requests. We ignore status requests, and only
+                // put beep requests into the queue.
                 let mut ctx = &mut self.ports[PORT_1];
-                ctx.tx_data = val;
-                // Special case for status requests from the keyboard
-                if val == 0x02 {
-                    ctx.stat = STS_RXR | STS_PER;
+
+                if (val & 0x08) != 0 {
+                    ctx.tx_data = val;
+                    ctx.next_tx = Instant::now() + ctx.char_delay;
+                    ctx.stat &= !(STS_TXE | STS_TXR);
+                    self.istat &= !ISTS_TBI;
                 }
             }
             IP_OPCR => {