diff options
Diffstat (limited to 'src/mess/drivers/pc9801.c')
-rw-r--r-- | src/mess/drivers/pc9801.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/src/mess/drivers/pc9801.c b/src/mess/drivers/pc9801.c index 6b84ecd0f94..85fb2a13a90 100644 --- a/src/mess/drivers/pc9801.c +++ b/src/mess/drivers/pc9801.c @@ -1351,13 +1351,13 @@ inline UINT16 pc9801_state::egc_do_partial_op(int plane, UINT16 src, UINT16 pat, { src = src_tmp << (dst_off - src_off); src |= m_egc.leftover[plane]; - m_egc.leftover[plane] = src_tmp >> (15 - (dst_off - src_off)); + m_egc.leftover[plane] = src_tmp >> (16 - (dst_off - src_off)); } else { src = src_tmp >> (src_off - dst_off); src |= m_egc.leftover[plane]; - m_egc.leftover[plane] = src_tmp << (15 - (src_off - dst_off)); + m_egc.leftover[plane] = src_tmp << (16 - (src_off - dst_off)); } for(int i = 7; i >= 0; i--) @@ -1380,16 +1380,28 @@ void pc9801_state::egc_blit_w(UINT32 offset, UINT16 data, UINT16 mem_mask) if((((m_egc.regs[2] >> 11) & 3) == 1) || ((((m_egc.regs[2] >> 11) & 3) == 2) && !BIT(m_egc.regs[2], 10))) { - // mask off the bits past the end of the blit - if(m_egc.count < 16) - mask &= dir ? ((1 << m_egc.count) - 1) : ~((1 << (16 - m_egc.count)) - 1); - + UINT16 end_mask = 0xffff, start_mask = 0xffff; // mask off the bits before the start if(m_egc.first) { m_egc.leftover[0] = m_egc.leftover[1] = m_egc.leftover[2] = m_egc.leftover[3] = 0; - mask &= dir ? ~((1 << dst_off) - 1) : ((1 << (16 - dst_off)) - 1); + start_mask = dir ? ~((1 << dst_off) - 1) : ((1 << (15 - dst_off)) - 1); + } + + // mask off the bits past the end of the blit + if(m_egc.count < 16) + { + end_mask = dir ? ((1 << m_egc.count) - 1) : ~((1 << (16 - m_egc.count)) - 1); + // if the blit is less than 16 bits, adjust the masks + if(start_mask != 0xffff) + { + if(dir) + end_mask <<= dst_off; + else + end_mask >>= (15 - dst_off); + } } + mask &= end_mask & start_mask; } for(int i = 0; i < 4; i++) |