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starrider: few more notes (nw)

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This commit is contained in:
Vas Crabb 2019-05-26 15:43:33 +10:00
parent 626b566fee
commit 987365c5c5
1 changed files with 10 additions and 2 deletions
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12
src/mame/drivers/starrider.cpp
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@ -138,6 +138,9 @@
Q ______------------____________------------____________------------______
LATCH ______________--------________________--------________________--------__
__----__----__----__----__----__----__----__----__----__----__----__----
/SRL --------____--------------------____--------------------____------------
4MHz ___---___---___---___---___---___---___---___---___---___---___---___---
2MHz ______------______------______------______------______------______------
Video RAM consists of 6 4416 16k*4 DRAMs at U25, U26, U41, U42, U55 and
U56. The CPU and DMA chips have their addressing mangled by the 6349
@ -170,10 +173,13 @@
U14.6 (active low) 1111x xxxx xxxxxxxx xxxxxxxx
U15.13 (active high) xxxxx xx11 xxxxxxxx xxxxxxxx (W)
U18.8 (active low) xxxxx xx10 xxxxxxxx xxxxxxxx (CPU access)
U46.3 /1E 11110 xxxx xxxxxxxx xxxxxxxx
U46.8 /1F 11111 xxxx xxxxxxxx xxxxxxxx
U46.11 (active low) 11110 xx01 xxxxxxxx xxxxxxxx
U33.8 (active low) 11001011 xxxxxxxx 0xcb00-0xcbff
@ -613,6 +619,8 @@ u16 sr_state::vgg_drams_map(u16 a) const
void sr_state::vgg_drams_w(offs_t offset, u8 data)
{
if (((m_main_page & 0x03) == 0x03) || (((m_main_page & 0x03) == 0x01) && ((m_vgg_image_page & 0x1f) == 0x1e)))
offset ^= 0x8000;
u16 const addr(vgg_drams_map(offset));
if ((offset & 0xc000) != 0xc000)
m_vgg_drams[addr] = data;
@ -621,7 +629,7 @@ void sr_state::vgg_drams_w(offs_t offset, u8 data)
void sr_state::vgg_impg_w(u8 data)
{
// 6 bits latched by U13 (74LS173) but only 5 bits used
m_vgg_image_page = data & 0x1f;
m_vgg_image_page = data & 0x3f;
}
void sr_state::vgg_xlate_w(u8 data)
@ -640,7 +648,7 @@ void sr_state::vgg_disable_w(u8 data)
void sr_state::vgg_color_palet_w(u8 data)
{
// all 8 bits latched by U94 (74LS374) but only 6 bits used
m_vgg_color_palet = data & 0x3f;
m_vgg_color_palet = data;
}