From 7bd685bfa30474e8af5675aa622a502ba2f18797 Mon Sep 17 00:00:00 2001
From: Oxore <oxore@protonmail.com>
Date: Mon, 18 Nov 2019 04:01:59 +0300
Subject: Implement LJMP instruction

---
 src/core.rs | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/core.rs b/src/core.rs
index 01ec71f..f239cdd 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -37,6 +37,7 @@ pub enum Operand {
     Register(Register),
     Reladdr(i8),
     Addr11(u16),
+    Addr16(u16),
 }
 
 #[derive(Debug, Clone)]
@@ -59,6 +60,7 @@ const RAM_OFFSET_R7: u8 = 0x07;
 
 const OPCODE_NOP: u8 = 0x00;
 const OPCODE_AJMP_P0: u8 = 0x01;
+const OPCODE_LJMP: u8 = 0x02;
 const OPCODE_AJMP_P1: u8 = 0x21;
 const OPCODE_AJMP_P2: u8 = 0x41;
 const OPCODE_AJMP_P3: u8 = 0x61;
@@ -102,6 +104,12 @@ const OP_LUT: [Isa8051Op; u8::max_value() as usize + 1] = {
         operand1: Some(Isa8051Operand::Addr11(0)),
         operand2: None,
     };
+    lut[OPCODE_LJMP as usize] = Isa8051Op {
+        opcode: Isa8051Opcode::Ljmp,
+        size: 3,
+        operand1: Some(Isa8051Operand::Addr16),
+        operand2: None,
+    };
     lut[OPCODE_AJMP_P1 as usize] = Isa8051Op {
         opcode: Isa8051Opcode::Ajmp,
         size: 2,
@@ -256,6 +264,7 @@ impl fmt::Display for Operand {
                 Operand::Register(r) => format!("{:?}", r),
                 Operand::Reladdr(rel) => format!("{}", rel),
                 Operand::Addr11(rel) => format!("{}", rel),
+                Operand::Addr16(rel) => format!("{}", rel),
             }
         )
     }
@@ -285,6 +294,7 @@ impl Operand {
             Operand::Register(_) => 0,
             Operand::Reladdr(_) => 1,
             Operand::Addr11(_) => 1,
+            Operand::Addr16(_) => 2,
         }
     }
 }
@@ -384,6 +394,16 @@ impl Core {
                     panic!("AJMP has no operand given")
                 }
             }
+            Isa8051Opcode::Ljmp => {
+                if let Some(operand) = op.operand1 {
+                    match operand {
+                        Operand::Addr16(addr) => self.ljmp(addr),
+                        _ => panic!("LJMP got incompatible operand"),
+                    }
+                } else {
+                    panic!("LJMP has no operand given")
+                }
+            }
         }
     }
 
@@ -411,7 +431,11 @@ impl Core {
     }
 
     fn ajmp(&mut self, pageaddr: u16) {
-        self.pc = (self.pc & !0x4FFu16) + pageaddr as u16;
+        self.pc = (self.pc & !0x4FFu16) + pageaddr;
+    }
+
+    fn ljmp(&mut self, pageaddr: u16) {
+        self.pc = pageaddr;
     }
 
     fn map_operand(&self, operand: Isa8051Operand, offset: usize) -> Operand {
@@ -427,6 +451,10 @@ impl Core {
             Isa8051Operand::Addr11(high) => Operand::Addr11(
                 self.rom.array[(self.pc as usize + offset)] as u16 + (u16::from(high) << 8),
             ),
+            Isa8051Operand::Addr16 => Operand::Addr16(
+                (u16::from(self.rom.array[(self.pc as usize + offset)]) << 8)
+                    + u16::from(self.rom.array[(self.pc as usize + offset + 1)]),
+            ),
         }
     }
 }
@@ -440,12 +468,14 @@ pub enum Isa8051Operand {
     Register(Register),
     Reladdr,
     Addr11(u8),
+    Addr16,
 }
 
 #[derive(Debug, Clone, Copy)]
 pub enum Isa8051Opcode {
     Nop,
     Ajmp,
+    Ljmp,
     Mov,
     Push,
     Pop,
-- 
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