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n68681: Return bits 6 and 7 of the input port register correctly. (nw)

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This commit is contained in:
R. Belmont 2014-03-08 03:49:28 +00:00
parent dd000a591a
commit b3c2e03a9f
2 changed files with 19 additions and 3 deletions
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18
src/emu/machine/n68681.c
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@ -130,6 +130,7 @@ void duartn68681_device::device_reset()
OPR = 0; /* Output Port Register */
CTR.d = 0; /* Counter/Timer Preset Value */
IP_last_state = 0; /* last state of IP bits */
m_read_vector = false;
// "reset clears internal registers (SRA, SRB, IMR, ISR, OPR, OPCR) puts OP0-7 in the high state, stops the counter/timer, and puts channels a/b in the inactive state"
write_outport(OPR ^ 0xff);
@ -166,6 +167,7 @@ void duartn68681_device::update_interrupts()
{
LOG(( "68681: Interrupt line not active (IMR & ISR = %02X)\n", ISR & IMR));
write_irq(CLEAR_LINE);
m_read_vector = false; // clear IACK too
}
};
@ -314,6 +316,18 @@ READ8_MEMBER( duartn68681_device::read )
{
r = IP_last_state;
}
r |= 0x80; // bit 7 is always set
// bit 6 is /IACK (note the active-low)
if (m_read_vector)
{
r &= ~0x40;
}
else
{
r |= 0x40;
}
break;
case 0x0e: /* Start counter command */
@ -523,14 +537,14 @@ WRITE_LINE_MEMBER( duartn68681_device::ip3_w )
WRITE_LINE_MEMBER( duartn68681_device::ip4_w )
{
UINT8 newIP = (IP_last_state & ~0x10) | (state == ASSERT_LINE) ? 0x10 : 0;
// TODO: special mode for ip4
// TODO: special mode for ip4 (Ch. A Rx clock)
IP_last_state = newIP;
}
WRITE_LINE_MEMBER( duartn68681_device::ip5_w )
{
UINT8 newIP = (IP_last_state & ~0x20) | (state == ASSERT_LINE) ? 0x20 : 0;
// TODO: special mode for ip5
// TODO: special mode for ip5 (Ch. B Tx clock)
IP_last_state = newIP;
}

4
src/emu/machine/n68681.h
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@ -109,7 +109,7 @@ public:
// API
DECLARE_READ8_HANDLER(read);
DECLARE_WRITE8_HANDLER(write);
UINT8 get_irq_vector() { return IVR; }
UINT8 get_irq_vector() { m_read_vector = true; return IVR; }
DECLARE_WRITE_LINE_MEMBER( rx_a_w ) { m_chanA->device_serial_interface::rx_w((UINT8)state); }
DECLARE_WRITE_LINE_MEMBER( rx_b_w ) { m_chanB->device_serial_interface::rx_w((UINT8)state); }
@ -152,6 +152,8 @@ private:
PAIR CTR; /* Counter/Timer Preset Value */
UINT8 IPCR; /* Input Port Control Register */
bool m_read_vector; // if this is read and IRQ is active, it counts as pulling IACK
/* state */
UINT8 IP_last_state; /* last state of IP bits */