hmcs40: fix possible issue with irq/lpu (nw)

src/devices/cpu/hmcs40/hmcs40.cpp

@@ -578,7 +578,7 @@ void hmcs40_cpu_device::execute_run()
 	while (m_icount > 0)
 	{
 		// LPU is handled 1 cycle later
-		if ((m_prev_op & 0x3e0) == 0x340)
+		if ((m_prev_op & 0x7e0) == 0x340)
 			m_pc = ((m_page << 6) | (m_pc & 0x3f)) & m_pcmask;
 
 		// remember previous state

src/devices/cpu/hmcs40/hmcs40op.cpp

@@ -465,7 +465,7 @@ void hmcs40_cpu_device::op_lpu()
 	if (m_s)
 		m_page = m_op & 0x1f;
 	else
-		m_op = 0; // fake nop
+		m_op |= 0x400; // indicate unhandled LPU
 }
 
 void hmcs40_cpu_device::op_tbr()

src/mame/drivers/hh_hmcs40.cpp

@@ -75,7 +75,7 @@
   - gckong random lockups (tap the jump button repeatedly): mcu stack overflow,
     works ok if stack levels is increased, 38800 B rev. has more stack levels?
     Or it could be a race condition: irq happening too late/early.
-  - epacman booting the game in demo mode, pacman should go straight to the
+  - epacman2 booting the game in demo mode, pacman should go straight to the
     upper-left power pill: mcu cycle/interrupt timing related
   - Though very uncommon when compared to games with LED/lamp display, some
     games may manipulate VFD plate brightness by strobing it longer/shorter,