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Make the emulated 6551's hardware reset state match the MOS datasheet.

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This commit is contained in:
Tim Allen 2023-05-29 17:34:59 +10:00 committed by Seth Morabito
parent b725fb5fdd
commit d076046f57
2 changed files with 29 additions and 0 deletions
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8
src/main/java/com/loomcom/symon/devices/Acia6551.java
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@ -53,6 +53,14 @@ public class Acia6551 extends Acia {
public Acia6551(int address) throws MemoryRangeException {
super(address, ACIA_SIZE, "ACIA");
// Figure 6 in the 6551 ACIA data sheet says the "hardware reset"
// state of the Control Register is all zeros.
setControlRegister(0b00000000);
// Figure 7 of the 6551 ACIA data sheet says the "hardware reset"
// state of the Command Register is zeros, but Transmitter Control
// is set to "interrupt disabled, ready to send".
setCommandRegister(0b00000010);
}
@Override

21
src/test/java/com/loomcom/symon/AciaTest.java
View File

@ -254,4 +254,25 @@ public class AciaTest {
assertEquals(0x08, acia.read(0x0001, true));
}
@Test
public void statusRegisterInitializedAtHardwareReset() throws Exception {
Acia6551 acia = new Acia6551(0x0000);
assertEquals(0x10, acia.read(0x0001, false));
}
@Test
public void commandRegisterInitializedAtHardwareReset() throws Exception {
Acia6551 acia = new Acia6551(0x0000);
assertEquals(0x02, acia.read(0x0002, false));
}
@Test
public void controlRegisterInitializedAtHardwareReset() throws Exception {
Acia6551 acia = new Acia6551(0x0000);
assertEquals(0x00, acia.read(0x0003, false));
}
}