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osborne1: Fix scrolling based on better understanding from schematics and document operation

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This commit is contained in:
Vas Crabb 2015-10-30 19:34:03 +11:00
parent f9b063306e
commit 3f919cb083
3 changed files with 41 additions and 26 deletions
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11
src/mame/drivers/osborne1.c
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@ -255,6 +255,9 @@ static MACHINE_CONFIG_START( osborne1, osborne1_state )
MCFG_PIA_CB2_HANDLER(DEVWRITELINE(IEEE488_TAG, ieee488_device, ren_w))
MCFG_PIA_IRQA_HANDLER(WRITELINE(osborne1_state, ieee_pia_irq_a_func))
MCFG_IEEE488_BUS_ADD()
MCFG_IEEE488_SRQ_CALLBACK(DEVWRITELINE("pia_0", pia6821_device, ca2_w))
MCFG_DEVICE_ADD("pia_1", PIA6821, 0)
MCFG_PIA_WRITEPA_HANDLER(WRITE8(osborne1_state, video_pia_port_a_w))
MCFG_PIA_WRITEPB_HANDLER(WRITE8(osborne1_state, video_pia_port_b_w))
@ -277,13 +280,11 @@ static MACHINE_CONFIG_START( osborne1, osborne1_state )
MCFG_FLOPPY_DRIVE_ADD("mb8877:0", osborne1_floppies, "525ssdd", floppy_image_device::default_floppy_formats)
MCFG_FLOPPY_DRIVE_ADD("mb8877:1", osborne1_floppies, "525ssdd", floppy_image_device::default_floppy_formats)
MCFG_IEEE488_BUS_ADD()
MCFG_IEEE488_SRQ_CALLBACK(DEVWRITELINE("pia_0", pia6821_device, ca2_w))
MCFG_SOFTWARE_LIST_ADD("flop_list","osborne1")
// internal ram
MCFG_RAM_ADD(RAM_TAG)
MCFG_RAM_DEFAULT_SIZE("68K") // 64bB main RAM and 4kbit video attribute RAM
MCFG_RAM_DEFAULT_SIZE("68K") // 64kB main RAM and 4kbit video attribute RAM
MCFG_SOFTWARE_LIST_ADD("flop_list","osborne1")
MACHINE_CONFIG_END

13
src/mame/includes/osborne1.h
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@ -100,11 +100,6 @@ public:
required_device<floppy_image_device> m_floppy0;
required_device<floppy_image_device> m_floppy1;
/* video related */
UINT8 m_resolution;
UINT8 m_hc_left;
UINT8 m_new_start_x;
UINT8 m_new_start_y;
emu_timer *m_video_timer;
UINT8 *m_p_chargen;
bool m_beep_state;
@ -149,6 +144,14 @@ protected:
UINT8 m_rom_mode;
UINT8 m_bit_9;
// video registers
UINT8 m_scroll_x;
UINT8 m_scroll_y;
// SCREEN-PAC registers
UINT8 m_resolution;
UINT8 m_hc_left;
// serial state
int m_acia_irq_state;
int m_acia_rxc_txc_state;

43
src/mame/machine/osborne1.c
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@ -86,7 +86,7 @@ WRITE8_MEMBER( osborne1_state::bank_2xxx_3xxx_w )
if ((offset & 0xC00) == 0x400) // SCREEN-PAC
{
m_resolution = data & 0x01;
m_hc_left = (data >> 1) & 0x01;
m_hc_left = (data & 0x02) ? 0 : 1;
}
if ((offset & 0xC00) == 0xC00) // Video PIA
m_pia1->write(space, offset & 0x03, data);
@ -202,20 +202,15 @@ WRITE_LINE_MEMBER( osborne1_state::ieee_pia_irq_a_func )
WRITE8_MEMBER( osborne1_state::video_pia_port_a_w )
{
m_scroll_x = data >> 1;
m_fdc->dden_w(BIT(data, 0));
data -= 0xea; // remove bias
m_new_start_x = (data >> 1);
if (m_new_start_x)
m_new_start_x--;
//logerror("Video pia port a write: %02X, density set to %s\n", data, data & 1 ? "FM" : "MFM" );
}
WRITE8_MEMBER( osborne1_state::video_pia_port_b_w )
{
m_new_start_y = data & 0x1F;
m_scroll_y = data & 0x1F;
m_beep_state = BIT(data, 5);
if (BIT(data, 6))
@ -232,8 +227,6 @@ WRITE8_MEMBER( osborne1_state::video_pia_port_b_w )
{
m_fdc->set_floppy(NULL);
}
//logerror("Video pia port b write: %02X\n", data );
}
WRITE_LINE_MEMBER( osborne1_state::video_pia_out_cb2_dummy )
@ -310,7 +303,7 @@ void osborne1_state::machine_reset()
update_acia_rxc_txc();
m_resolution = 0;
m_hc_left = 0;
m_hc_left = 1;
m_p_chargen = memregion( "chargen" )->base();
for (unsigned i = 0; i < 0x1000; i++)
@ -344,10 +337,28 @@ TIMER_CALLBACK_MEMBER(osborne1_state::video_callback)
{
ra = y % 10;
// Draw a line of the display
bool const hires = m_screen_pac & m_resolution;
UINT16 const row = (m_new_start_y + (y/10)) * 128 & 0xF80;
UINT16 const col = (m_new_start_x & (hires ? 0x60 : 0x7F)) - ((hires && m_hc_left) ? 8 : 0);
UINT16 *p = &m_bitmap.pix16(y);
bool const hires = m_screen_pac & m_resolution;
UINT16 const row = ((m_scroll_y + (y / 10)) << 7) & 0xF80;
// The derivation of the initial column is not obvious. The 7-bit
// column counter is preloaded near the beginning of the horizontal
// blank period. The initial column is offset by the number of
// character clock periods in the horizontal blank period minus one
// because it latches the value before it's displayed. Using the
// standard video display, there are 12 character clock periods in
// the horizontal blank period, so subtracting 1 gives 0x0B. Using
// the SCREEN-PAC's high-resolution mode, the character clock is
// twice the frequency giving 24 character clock periods in the
// horizontal blanking period, so subtracting 1 gives 0x17. Using
// the standard video display, the column counter is preloaded with
// the high 7 bits of the value from PIA1 PORTB. The SCREEN-PAC
// takes the two high bits of this value, but sets the low five bits
// to a fixed value of 1 or 9 depending on the value of the HC-LEFT
// signal (set by bit 1 of the value written to 0x2400). Of course
// it depends on the value wrapping around to zero when it counts
// past 0x7F
UINT16 const col = hires ? ((m_scroll_x & 0x60) + (m_hc_left ? 0x09 : 0x01) + 0x17) : (m_scroll_x + 0x0B);
for ( UINT16 x = 0; x < (hires ? 104 : 52); x++ )
{