From b561b470c145ccb9711d2852058b7dfdf25adf1d Mon Sep 17 00:00:00 2001 From: AJR Date: Fri, 11 May 2018 09:18:00 -0400 Subject: [PATCH] lrw80, radionic: Better conjectures regarding clocks (nw) --- src/mame/drivers/trs80.cpp | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/mame/drivers/trs80.cpp b/src/mame/drivers/trs80.cpp index 95fb05e333b..761fc4df16f 100644 --- a/src/mame/drivers/trs80.cpp +++ b/src/mame/drivers/trs80.cpp @@ -728,7 +728,7 @@ MACHINE_CONFIG_START(trs80_state::lnw80) MCFG_PALETTE_INIT_OWNER(trs80_state,lnw80) MCFG_SCREEN_MODIFY("screen") MCFG_SCREEN_RAW_PARAMS(3.579545_MHz_XTAL * 3, 682, 0, 480, 264, 0, 192) // 10.738MHz generated by tank circuit (top left of page 2 of schematics) - // LNW80 Theory of Operations gives H and V periods as 15.750kHz and 59.66Hz, which don't seem exactly divisible + // LNW80 Theory of Operations gives H and V periods as 15.750kHz and 59.66Hz, probably due to rounding the calculated ~15.7468kHz to 4 figures MCFG_SCREEN_UPDATE_DRIVER(trs80_state, screen_update_lnw80) MACHINE_CONFIG_END @@ -736,7 +736,9 @@ MACHINE_CONFIG_START(trs80_state::radionic) model1(config); MCFG_DEVICE_MODIFY("maincpu") MCFG_DEVICE_CLOCK(12_MHz_XTAL / 6) // or 3.579MHz / 2 (selectable?) - // Komtek I "User Friendly Manual" calls for "Z80 running at 1.97 MHz." Schematics mark XTAL as 12 MHz, but is that rounded off? + // Komtek I "User Friendly Manual" calls for "Z80 running at 1.97 MHz." This likely refers to an alternate NTSC version + // whose master clock was approximately 11.8005 MHz (6 times ~1.966 MHz and 750 times 15.734 kHz). Though the schematics + // provide the main XTAL frequency as 12 MHz, that they also include a 3.579 MHz XTAL suggests this possibility. MCFG_DEVICE_PERIODIC_INT_DRIVER(trs80_state, nmi_line_pulse, 12_MHz_XTAL / 12 / 16384) MCFG_SCREEN_MODIFY("screen")