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// AVR-Dx NVMCTRL + Mapped EEPROM
// EEPROM is memory-mapped at 0x1400-0x14FF and accessed via NVMCTRL commands.
import type { CPU } from 'avr8js/cpu/cpu';
import type { AVRDxCCP } from './avrdx-ccp';
const CTRLA = 0x0000;
// const CTRLB = 0x0001;
// const STATUS = 0x0002;
// const INTCTRL = 0x0003;
// const INTFLAGS = 0x0004;
// const DATAL = 0x0006;
// const DATAH = 0x0007;
// const ADDR0 = 0x0008;
// const ADDR1 = 0x0009;
// const ADDR2 = 0x000A;
// const ADDR3 = 0x000B;
// CMD values
const CMD_NONE_gc = 0x00;
const CMD_NOOP_gc = 0x01;
// const CMD_FLWR_gc = 0x02;
// const CMD_FLPER_gc = 0x08;
// const CMD_FLMPER2_gc = 0x09;
// const CMD_FLMPER4_gc = 0x0A;
// const CMD_FLMPER8_gc = 0x0B;
// const CMD_FLMPER16_gc = 0x0C;
// const CMD_FLMPER32_gc = 0x0D;
const CMD_EEWR_gc = 0x12;
const CMD_EEERWR_gc = 0x13;
const CMD_EEBER_gc = 0x18;
// const CMD_EEMBER2_gc = 0x19;
// const CMD_EEMBER4_gc = 0x1A;
// const CMD_EEMBER8_gc = 0x1B;
// const CMD_EEMBER16_gc = 0x1C;
// const CMD_EEMBER32_gc = 0x1D;
export class AVRDxNVMCTRL {
readonly eeprom: Uint8Array;
/** Page buffer for EEPROM writes (tracks which bytes have been written) */
private pageBuffer: Uint8Array;
private pageBufferDirty: Uint8Array;
constructor(cpu: CPU, base: number, start: number, private size: number, private ccp: AVRDxCCP, init: undefined | Uint8Array = undefined) {
this.eeprom = new Uint8Array(size);
this.pageBuffer = new Uint8Array(size);
this.pageBufferDirty = new Uint8Array(size);
this.eeprom.fill(0xFF);
if (init) this.loadEeprom(init);
// CTRLA - CCP protected, executes NVM commands
cpu.writeHooks[base + CTRLA] = (value: number) => {
if (this.ccp.isUnlocked()) {
cpu.data[base + CTRLA] = value;
this.executeCommand(value);
}
return true;
};
// Mapped EEPROM read hooks (0x1400-0x14FF)
for (let i = 0; i < size; i++) {
cpu.readHooks[start + i] = () => this.eeprom[i];
// Writes to mapped EEPROM go to the page buffer
cpu.writeHooks[start + i] = (value: number) => {
this.pageBuffer[i] = value;
this.pageBufferDirty[i] = 1;
// Check the current active command
const cmd = cpu.data[base + CTRLA];
if (cmd === CMD_EEERWR_gc) {
// Erase+write: replace byte directly
this.eeprom[i] = value;
this.pageBufferDirty[i] = 0;
} else if (cmd === CMD_EEWR_gc) {
// Write-only: AND with existing data (can only clear bits)
this.eeprom[i] &= value;
this.pageBufferDirty[i] = 0;
}
return true;
};
}
}
loadEeprom(data: Uint8Array) {
this.eeprom.set(data.subarray(0, this.size));
}
private executeCommand(cmd: number) {
switch (cmd) {
case CMD_NONE_gc:
case CMD_NOOP_gc:
this.pageBufferDirty.fill(0);
break;
case CMD_EEWR_gc:
// Write-only mode: subsequent mapped EEPROM writes AND with existing data.
// Actual writes happen in the mapped EEPROM write hooks.
// Don't clear command — it stays active until NONE/NOOP.
break;
case CMD_EEERWR_gc:
// Erase+write mode: subsequent mapped EEPROM writes replace data directly.
// Actual writes happen in the mapped EEPROM write hooks.
// Don't clear command — it stays active until NONE/NOOP.
break;
case CMD_EEBER_gc:
// Erase EEPROM page (the page containing the address in ADDR)
// For simplicity, erase the whole EEPROM
// TODO: figure out page size
this.eeprom.fill(0xFF);
this.pageBufferDirty.fill(0);
break;
default:
// TODO: implement other commands (if needed)
break;
}
}
}
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