dingusppc/devices/serial/escc.cpp

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/*
DingusPPC - The Experimental PowerPC Macintosh emulator
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Copyright (C) 2018-22 divingkatae and maximum
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(theweirdo) spatium
(Contact divingkatae#1017 or powermax#2286 on Discord for more info)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/** @file Enhanced Serial Communications Controller (ESCC) emulation. */
#include "escc.h"
#include <loguru.hpp>
#include <cinttypes>
#include <memory>
EsccController::EsccController()
{
this->ch_a = std::unique_ptr<EsccChannel> (new EsccChannel("A"));
this->ch_b = std::unique_ptr<EsccChannel> (new EsccChannel("B"));
this->reg_ptr = 0;
}
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void EsccController::reset()
{
this->master_int_cntrl &= 0xFC;
this->master_int_cntrl |= 0xC0;
this->ch_a->reset(true);
this->ch_b->reset(true);
}
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uint8_t EsccController::read(uint8_t reg_offset)
{
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uint8_t result = 0;
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switch(reg_offset) {
case EsccReg::Port_B_Cmd:
LOG_F(9, "ESCC: reading Port B register RR%d", this->reg_ptr);
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if (this->reg_ptr == 2) {
// TODO: implement interrupt vector modifications
result = this->int_vec;
} else {
result = this->ch_b->read_reg(this->reg_ptr);
}
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this->reg_ptr = 0;
break;
case EsccReg::Port_A_Cmd:
LOG_F(9, "ESCC: reading Port A register RR%d", this->reg_ptr);
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if (this->reg_ptr == 2) {
return this->int_vec;
} else {
return this->ch_a->read_reg(this->reg_ptr);
}
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this->reg_ptr = 0;
break;
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case EsccReg::Port_B_Data:
return this->ch_b->receive_byte();
case EsccReg::Port_A_Data:
return this->ch_a->receive_byte();
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default:
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LOG_F(9, "ESCC: reading from unimplemented register %d", reg_offset);
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}
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return result;
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}
void EsccController::write(uint8_t reg_offset, uint8_t value)
{
switch(reg_offset) {
case EsccReg::Port_B_Cmd:
this->write_internal(this->ch_b.get(), value);
break;
case EsccReg::Port_A_Cmd:
this->write_internal(this->ch_a.get(), value);
break;
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case EsccReg::Port_B_Data:
this->ch_b->send_byte(value);
break;
case EsccReg::Port_A_Data:
this->ch_a->send_byte(value);
break;
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default:
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LOG_F(9, "ESCC: writing 0x%X to unimplemented register %d", value, reg_offset);
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}
}
void EsccController::write_internal(EsccChannel *ch, uint8_t value)
{
if (this->reg_ptr) {
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// chip-specific registers
if (this->reg_ptr == 9) {
// see if some reset is requested
switch(value & 0xC0) {
case RESET_CH_B:
this->master_int_cntrl &= 0xDF;
this->ch_b->reset(false);
break;
case RESET_CH_A:
this->master_int_cntrl &= 0xDF;
this->ch_a->reset(false);
break;
case RESET_ESCC:
this->reset();
break;
}
this->master_int_cntrl = value & 0x3F;
} else if (this->reg_ptr == 2) {
this->int_vec = value;
} else { // channel-specific registers
ch->write_reg(this->reg_ptr, value);
}
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this->reg_ptr = 0;
} else {
this->reg_ptr = value & 7;
switch(value >> 3) {
case WR0Cmd::Point_High:
this->reg_ptr |= 8;
break;
}
}
}
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// ======================== ESCC Channel methods ==============================
void EsccChannel::reset(bool hw_reset)
{
this->write_regs[1] &= 0x24;
this->write_regs[3] &= 0xFE;
this->write_regs[4] |= 0x04;
this->write_regs[5] &= 0x61;
this->write_regs[15] = 0xF8;
this->read_regs[0] &= 0x3C;
this->read_regs[0] |= 0x44;
this->read_regs[1] = 0x06;
this->read_regs[3] = 0x00;
this->read_regs[10] = 0x00;
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// initialize DPLL
this->dpll_active = 0;
this->dpll_mode = DpllMode::NRZI;
this->dpll_clock_src = 0;
// initialize Baud Rate Generator (BRG)
this->brg_active = 0;
this->brg_clock_src = 0;
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if (hw_reset) {
this->write_regs[10] = 0;
this->write_regs[11] = 8;
this->write_regs[14] &= 0xC0;
this->write_regs[14] |= 0x20;
} else {
this->write_regs[10] &= 0x60;
this->write_regs[14] &= 0xC3;
this->write_regs[14] |= 0x20;
}
}
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void EsccChannel::write_reg(int reg_num, uint8_t value)
{
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switch (reg_num) {
case 3:
if (value & 0x11) {
if ((this->write_regs[3] ^ value) & 0x10) {
this->write_regs[3] |= 0x10;
this->read_regs[0] |= 0x10; // set SYNC_HUNT flag
LOG_F(9, "ESCC: Hunt mode entered.");
}
if (value & 1) {
this->write_regs[3] |= 0x1;
LOG_F(9, "ESCC: receiver enabled.");
}
}
this->write_regs[3] = (this->write_regs[3] & 0x11) | (value & 0xEE);
return;
case 7:
if (this->write_regs[15] & 1) {
this->wr7_enh = value;
return;
}
break;
case 14:
switch (value >> 5) {
case DPLL_ENTER_SRC_MODE:
this->dpll_active = 1;
this->read_regs[10] &= 0x3F;
break;
case DPLL_DISABLE:
this->dpll_active = 0;
// fallthrough
case DPLL_RST_MISSING_CLK:
this->read_regs[10] &= 0x3F;
break;
case DPLL_SET_SRC_BGR:
this->dpll_clock_src = 0;
break;
case DPLL_SET_SRC_RTXC:
this->dpll_clock_src = 1;
break;
case DPLL_SET_FM_MODE:
this->dpll_mode = DpllMode::FM;
break;
case DPLL_SET_NRZI_MODE:
this->dpll_mode = DpllMode::NRZI;
break;
default:
LOG_F(WARNING, "ESCC: unimplemented DPLL command %d", value >> 5);
}
if (value & 0x1C) { // Local Loopback, Auto Echo DTR/REQ bits set
LOG_F(WARNING, "ESCC: unexpected value in WR14 = 0x%X", value);
}
if (this->brg_active ^ (value & 1)) {
this->brg_active = value & 1;
LOG_F(9, "ESCC: BRG %s", this->brg_active ? "enabled" : "disabled");
}
return;
}
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this->write_regs[reg_num] = value;
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}
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uint8_t EsccChannel::read_reg(int reg_num)
{
return this->read_regs[reg_num];
}
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void EsccChannel::send_byte(uint8_t value)
{
// Put one byte into the Data FIFO
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}
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uint8_t EsccChannel::receive_byte()
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{
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// Remove one byte from the Receive FIFO
return 0xFF;
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}