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Z80scc: Implement RTxC clock source (#12050)

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Fixes serial emulation at 115200 or 230400bps.

Co-authored-by: Colin Leroy-Mira <colin.leroy-mira@sigfox.com>
This commit is contained in:
Colin Leroy-Mira 2024-02-24 03:28:33 +01:00 committed by GitHub
parent d37771ec53
commit 83c82598e6
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GPG key ID: B5690EEEBB952194
2 changed files with 33 additions and 7 deletions
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39
src/devices/machine/z80scc.cpp
View file

@ -2092,7 +2092,7 @@ void z80scc_channel::do_sccreg_wr11(uint8_t data)
/RTxC pin.*/
switch (data & WR11_RCVCLK_SRC_MASK)
{
case WR11_RCVCLK_SRC_RTXC: LOG("Receive clock source is RTxC - not implemented\n"); break;
case WR11_RCVCLK_SRC_RTXC: LOG("Receive clock source is RTxC\n"); break;
case WR11_RCVCLK_SRC_TRXC: LOG("Receive clock source is TRxC - not implemented\n"); break;
case WR11_RCVCLK_SRC_BR: LOG("Receive clock source is Baudrate Generator\n"); break;
case WR11_RCVCLK_SRC_DPLL: LOG("Receive clock source is DPLL - not implemented\n"); break;
@ -2106,7 +2106,7 @@ void z80scc_channel::do_sccreg_wr11(uint8_t data)
source of the transmit clocks.*/
switch (data & WR11_TRACLK_SRC_MASK)
{
case WR11_TRACLK_SRC_RTXC: LOG("Transmit clock source is RTxC - not implemented\n"); break;
case WR11_TRACLK_SRC_RTXC: LOG("Transmit clock source is RTxC\n"); break;
case WR11_TRACLK_SRC_TRXC: LOG("Transmit clock source is TRxC - not implemented\n"); break;
case WR11_TRACLK_SRC_BR: LOG("Transmit clock source is Baudrate Generator\n"); break;
case WR11_TRACLK_SRC_DPLL: LOG("Transmit clock source is DPLL - not implemented\n"); break;
@ -2136,6 +2136,8 @@ void z80scc_channel::do_sccreg_wr11(uint8_t data)
}
else
LOG("TRxC pin is Input\n");
update_serial();
}
/*WR12 contains the lower byte of the time constant for the baud rate generator. The time constant
@ -2795,18 +2797,30 @@ unsigned int z80scc_channel::get_brg_rate()
if (m_wr14 & WR14_BRG_SOURCE) // Do we use the PCLK as baudrate source
{
rate = owner()->clock() / (brg_const == 0 ? 1 : brg_const);
LOG(" - Source bit rate (%d) = PCLK (%d) / (%d)\n", rate, owner()->clock(), brg_const);
LOG(" - BRG Source bit rate (%d) = PCLK (%d) / (%d)\n", rate, owner()->clock(), brg_const);
}
else // Else we use the RTxC as BRG source
{
unsigned int source = (m_index == z80scc_device::CHANNEL_A) ? m_uart->m_rxca : m_uart->m_rxcb;
rate = source / (brg_const == 0 ? 1 : brg_const);
LOG(" - Source bit rate (%d) = RTxC (%d) / (%d)\n", rate, source, brg_const);
LOG(" - BRG Source bit rate (%d) = RTxC (%d) / (%d)\n", rate, source, brg_const);
}
return (rate / (2 * get_clock_mode()));
}
//-------------------------------------------------
// get_rtxc_rate
//-------------------------------------------------
unsigned int z80scc_channel::get_rtxc_rate()
{
unsigned int rate;
unsigned int source = (m_index == z80scc_device::CHANNEL_A) ? m_uart->m_rxca : m_uart->m_rxcb;
rate = source / get_clock_mode();
LOG(" - RTxC Source bit rate (%d) = RTxC (%d) / (%d)\n", rate, source, get_clock_mode());
return rate;
}
void z80scc_channel::update_baudtimer()
{
unsigned int rate;
@ -2893,9 +2907,20 @@ void z80scc_channel::update_serial()
}
else
{
LOG("- BRG disabled\n");
set_rcv_rate(0);
set_tra_rate(0);
if ((m_wr11 & WR11_RCVCLK_SRC_MASK) == WR11_RCVCLK_SRC_RTXC &&
(m_wr11 & WR11_TRACLK_SRC_MASK) == WR11_TRACLK_SRC_RTXC)
{
m_brg_rate = get_rtxc_rate();
LOG("- BRG disabled, clock source RTxC (rate %d, clock %d)\n", m_brg_rate, get_clock_mode());
set_rcv_rate(m_brg_rate);
set_tra_rate(m_brg_rate);
}
else
{
LOG("- BRG disabled and RX/TX clock sources differ, unimplemented: stopping\n");
set_rcv_rate(0);
set_tra_rate(0);
}
}
// TODO: Check registers for use of RTxC and TRxC, if used as direct Tx and/or Rx clocks set them to value as programmed
// in m_uart->txca/txcb and rxca/rxcb respectivelly

1
src/devices/machine/z80scc.h
View file

@ -233,6 +233,7 @@ protected:
virtual void device_reset() override;
unsigned int get_brg_rate();
unsigned int get_rtxc_rate();
void update_baudtimer();
void scc_register_write(uint8_t reg, uint8_t data);