feat: initial implementation of USART

#6

1 files changed, 60 insertions, 0 deletions

diff --git a/src/usart.spec.ts b/src/usart.spec.ts
new file mode 100644
index 0000000..230709f
--- /dev/null
+++ b/src/usart.spec.ts
@@ -0,0 +1,60 @@
+import { CPU } from './cpu';
+import { AVRUSART, usart0Config } from './usart';
+
+const FREQ_16MHZ = 16e6;
+const FREQ_11_0529MHZ = 11059200;
+
+describe('USART', () => {
+  it('should correctly calculate the baudRate from UBRR', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_11_0529MHZ);
+    cpu.writeData(0xc5, 0); // UBRR0H <- 0
+    cpu.writeData(0xc4, 5); // UBRR0L <- 5
+    expect(usart.baudRate).toEqual(115200);
+  });
+
+  it('should correctly calculate the baudRate from UBRR in double-speed mode', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc5, 3); // UBRR0H <- 3
+    cpu.writeData(0xc4, 64); // UBRR0L <- 64
+    cpu.writeData(0xc0, 2); // UCSR0A: U2X0
+    expect(usart.baudRate).toEqual(2400);
+  });
+
+  it('should return 5-bits per byte when UCSZ = 0', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc0, 0);
+    expect(usart.bitsPerChar).toEqual(5);
+  });
+
+  it('should return 6-bits per byte when UCSZ = 1', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc0, 0x2);
+    expect(usart.bitsPerChar).toEqual(6);
+  });
+
+  it('should return 7-bits per byte when UCSZ = 2', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc0, 0x4);
+    expect(usart.bitsPerChar).toEqual(7);
+  });
+
+  it('should return 8-bits per byte when UCSZ = 3', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc0, 0x6);
+    expect(usart.bitsPerChar).toEqual(8);
+  });
+
+  it('should return 9-bits per byte when UCSZ = 7', () => {
+    const cpu = new CPU(new Uint16Array(1024));
+    const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+    cpu.writeData(0xc0, 0x6);
+    cpu.writeData(0xc1, 0x4);
+    expect(usart.bitsPerChar).toEqual(9);
+  });
+});