150 lines
3.5 KiB
JavaScript
150 lines
3.5 KiB
JavaScript
"use strict";
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/**
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* @constructor
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*/
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function DMA(dev)
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{
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var io = dev.io,
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memory = dev.memory,
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channels = [
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{ address: 0, count: 0 },
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{ address: 0, count: 0 },
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{ address: 0, count: 0 },
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{ address: 0, count: 0 }
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],
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lsb_msb_flipflop = 0;
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io.register_write(0x04, port_write.bind(0, 0x04));
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io.register_write(0x05, port_write.bind(0, 0x05));
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io.register_write(0x0A, portA_write);
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io.register_write(0x0B, portB_write);
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io.register_write(0x0C, portC_write);
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io.register_write(0x81, port81_write);
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function port_write(port, data_byte)
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{
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dbg_log("port " + port + " write " + data_byte, LOG_DMA);
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if(port < 8)
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{
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var channel = port >> 1;
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if(port & 1)
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{
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channels[channel].count = flipflop_get(channels[channel].count, data_byte);
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}
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else
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{
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channels[channel].address = flipflop_get(channels[channel].address, data_byte);
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}
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}
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};
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function port_read(port)
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{
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if(port < 8)
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{
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var channel = port >> 1;
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if(port & 1)
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{
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return channels[channel].count;
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}
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else
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{
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// Bug?
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return channels[channel].address;
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}
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}
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else
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{
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dbg_log("port " + h(port) + " read", LOG_DMA);
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}
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};
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function portA_write(data_byte)
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{
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dbg_log("port A write: " + h(data_byte), LOG_DMA);
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};
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function portB_write(data_byte)
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{
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dbg_log("port B write: " + h(data_byte), LOG_DMA);
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};
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function portC_write(data_byte)
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{
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lsb_msb_flipflop = 0;
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}
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function port81_write(data_byte)
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{
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channels[2].address = channels[2].address & 0xFFFF | data_byte << 16;
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}
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// read data, write to memory
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this.do_read = function(buffer, start, len, channel, fn)
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{
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var read_count = channels[channel].count,
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addr = channels[channel].address;
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dbg_log("DMA write channel " + channel, LOG_DMA);
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dbg_log("to " + h(addr) + " len " + h(read_count), LOG_DMA);
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if(len < read_count)
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{
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dbg_log("DMA should read more than provided: " + h(len) + " " + h(read_count), LOG_DMA);
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}
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channels[channel].address += len;
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buffer.get(start, len, function(data)
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{
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memory.write_blob(data, addr);
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fn();
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});
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};
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// write data, read memory
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this.do_write = function(buffer, start, len, channel, fn)
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{
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var read_count = channels[channel].count,
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addr = channels[channel].address;
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dbg_log("DMA write channel " + channel, LOG_DMA);
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dbg_log("to " + h(addr) + " len " + h(read_count), LOG_DMA);
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dbg_log(channels[channel], LOG_DMA);
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if(len < read_count)
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{
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dbg_log("DMA should read more than provided", LOG_DMA);
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}
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buffer.set(start,
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new Uint8Array(memory.buffer, addr, read_count + 1),
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function() {
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fn();
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}
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);
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}
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function flipflop_get(old_dword, new_byte)
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{
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lsb_msb_flipflop ^= 1;
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if(lsb_msb_flipflop)
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{
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// low byte
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return old_dword & ~0xFF | new_byte;
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}
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else
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{
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// high byte
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return old_dword & ~0xFF00 | new_byte << 8;
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}
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}
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}
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