m68hc05: SCI BAUD Register

This allows r/w and reset behavior for the BAUD register. Implementation of the SCI depends on these bytes.

Reference: mc68hc05c8a and MC68HC05C4 datasheets.

Author: Vincent-Halver

src/devices/cpu/m6805/m68hc05.cpp

@@ -160,6 +160,7 @@ m68hc05_device::m68hc05_device(
 	, m_port_irq_state(false)
 	, m_irq_line_state(false)
 	, m_irq_latch(0)
+	, m_baud(0x00)
 	, m_sccr1(0x00)
 	, m_tcmp_cb(*this)
 	, m_tcap_state(false)
@@ -412,6 +413,16 @@ u8 m68hc05_device::timer_r(offs_t offset)
 }
 
 
+u8 m68hc05_device::baud_r()
+{
+	return m_baud & 0x37;
+}
+
+void m68hc05_device::baud_w(u8 data)
+{
+	m_baud = data & 0x37;
+}
+
 u8 m68hc05_device::sccr1_r()
 {
 	return m_sccr1 & 0xd1;
@@ -490,6 +501,7 @@ void m68hc05_device::device_start()
 	save_item(NAME(m_trl_buf));
 	save_item(NAME(m_trl_latched));
 
+	save_item(NAME(m_baud));
 	save_item(NAME(m_sccr1));
 	// save COP watchdogs
 	save_item(NAME(m_pcop_cnt));
@@ -533,6 +545,9 @@ void m68hc05_device::device_reset()
 	m_irq_latch = 0;
 	update_port_irq();
 
+	// SCI reset
+	m_baud &= 0x07;
+
 	// timer reset
 	m_tcr &= 0x02;
 	m_tsr_seen = 0x00;
@@ -715,6 +730,7 @@ void m68hc05_device::add_port_state(std::array<bool, PORT_COUNT> const &ddr)
 
 void m68hc05_device::add_sci_state()
 {
+	state_add(M68HC05_BAUD, "BAUD", m_baud).mask(0x37);
 	state_add(M68HC05_SCCR1, "SCCR1", m_sccr1).mask(0xd1);
 }
 
@@ -801,7 +817,7 @@ void m68hc05c4_device::c4_map(address_map &map)
 	// 0x000a SPCR
 	// 0x000b SPSR
 	// 0x000c SPDR
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc05c4_device::baud_r), FUNC(m68hc05c4_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc05c4_device::sccr1_r), FUNC(m68hc05c4_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR
@@ -869,7 +885,7 @@ void m68hc05c8_device::c8_map(address_map &map)
 	// 0x000a SPCR
 	// 0x000b SPSR
 	// 0x000c SPDR
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc05c8_device::baud_r), FUNC(m68hc05c8_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc05c8_device::sccr1_r), FUNC(m68hc05c8_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR
@@ -937,7 +953,7 @@ void m68hc705c4a_device::c4a_map(address_map &map)
 	// 0x000a SPCR
 	// 0x000b SPSR
 	// 0x000c SPDR
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc705c4a_device::baud_r), FUNC(m68hc705c4a_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc705c4a_device::sccr1_r), FUNC(m68hc705c4a_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR
@@ -1031,7 +1047,7 @@ void m68hc705c8a_device::c8a_map(address_map &map)
 	// 0x000a SPCR
 	// 0x000b SPSR
 	// 0x000c SPDR
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc705c8a_device::baud_r), FUNC(m68hc705c8a_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc705c8a_device::sccr1_r), FUNC(m68hc705c8a_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR
@@ -1226,7 +1242,7 @@ void m68hc05l9_device::l9_map(address_map &map)
 	// 0x0009-0x000a configuration
 	// 0x000b minute alarm
 	// 0x000c hour alarm
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc05l9_device::baud_r), FUNC(m68hc05l9_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc05l9_device::sccr1_r), FUNC(m68hc05l9_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR
@@ -1299,7 +1315,7 @@ void m68hc05l11_device::l11_map(address_map &map)
 	// 0x000a port F direction
 	// 0x000b minute alarm
 	// 0x000c hour alarm
-	// 0x000d BAUD
+	map(0x000d, 0x000d).rw(FUNC(m68hc05l11_device::baud_r), FUNC(m68hc05l11_device::baud_w));
 	map(0x000e, 0x000e).rw(FUNC(m68hc05l11_device::sccr1_r), FUNC(m68hc05l11_device::sccr1_w));
 	// 0x000f SCCR2
 	// 0x0010 SCSR

src/devices/cpu/m6805/m68hc05.h

@@ -72,6 +72,7 @@ class m68hc05_device : public m6805_base_device
 		M68HC05_PS,
 		M68HC05_TR,
 
+		M68HC05_BAUD,
 		M68HC05_SCCR1,
 
 		M68HC05_COPRST,
@@ -110,6 +111,8 @@ class m68hc05_device : public m6805_base_device
 	void ocr_w(offs_t offset, u8 data);
 	u8 timer_r(offs_t offset);
 
+	u8 baud_r();
+	void baud_w(u8 data);
 	u8 sccr1_r();
 	void sccr1_w(u8 data);
 	void set_ncope(bool state) { m_ncope = state ? 1 : 0; }
@@ -168,6 +171,7 @@ class m68hc05_device : public m6805_base_device
 	u8                  m_irq_latch;
 
 	// serial communications interface
+	u8                  m_baud;
 	u8                  m_sccr1;
 	// timer/counter
 	devcb_write_line    m_tcmp_cb;