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heathkit/tlb.cpp: Fix GP-19 graphics mode display #11534

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merged 1 commit into from Sep 8, 2023
Merged

heathkit/tlb.cpp: Fix GP-19 graphics mode display #11534

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15 changes: 5 additions & 10 deletions src/mame/heathkit/tlb.cpp
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Expand Up @@ -17,12 +17,6 @@
TODO:
- INS8250 needs to implement "Set Break" (LCR, bit 6) before Break key
will function as expected.
- 49/50 row mode does not work when DOT clocks are programmed as documented
in the manual. It does work when DOT clock is fixed at the 20.282 MHz
rate.
- In 49/50 row mode, character descenders are cut off.
- fix GP-19 graphics mode only showing the top half of the image (on the
visible screen).

****************************************************************************/
/***************************************************************************
Expand Down Expand Up @@ -1114,7 +1108,7 @@ void heath_gp19_tlb_device::mem_map(address_map &map)
// ROMs 1, 2, 3
map(0x0000, 0x02fff).rom();

// Optional external board - Program ROM 4, external I/O
// Optional external board - Program ROM 4(not aware if any ever existed), external I/O
// map(0x3000, 0x03fff).rom();

map(0x4000, 0x40ff).mirror(0x3f00).ram();
Expand All @@ -1133,7 +1127,7 @@ void heath_gp19_tlb_device::io_map(address_map &map)
// Switch on GP-19 board
map(0x70, 0x70).mirror(0x07).portr("SW1");

// Optional Auxiliary I/O connector
// Optional Auxiliary I/O connector(not aware if any ever existed)
// map(0x78, 0x78).mirror(0x07);
}

Expand Down Expand Up @@ -1183,7 +1177,7 @@ MC6845_UPDATE_ROW(heath_gp19_tlb_device::crtc_update_row)
{
for (int x = 0; x < x_count; x++)
{
uint8_t const gfx = m_p_videoram[(ma + x) & 0x3fff] ^ screen_inv;
uint8_t const gfx = m_p_videoram[((ma << 1) + ( ra * x_count ) + x) & 0x3fff] ^ screen_inv;

for (int b = 0; 8 > b; ++b)
{
Expand All @@ -1193,6 +1187,8 @@ MC6845_UPDATE_ROW(heath_gp19_tlb_device::crtc_update_row)
}
else
{
uint16_t base = m_char_gen_a11 ? 0x800 : 0x0;

for (int x = 0; x < x_count; x++)
{
uint8_t inv = (x == cursor_x) ? 0xff : 0;
Expand All @@ -1207,7 +1203,6 @@ MC6845_UPDATE_ROW(heath_gp19_tlb_device::crtc_update_row)
inv ^= screen_inv;

// select proper character set
uint16_t base = m_char_gen_a11 ? 0x800 : 0x0;
uint8_t const gfx = m_p_chargen[base | (chr << 4) | ra] ^ inv;

// Display a scanline of a character (8 pixels)
Expand Down