# HG changeset patch # User Paul Boddie # Date 1644680538 -3600 # Node ID bb29b264d9b9040ae6d64e3c324aa9f02923aa95 # Parent c1e9c8102e395a41a985079e5ddbd8e62bd4fee2 Changed the NMI signal buffering to match the circuit diagram, on the advice of the "Acorn Information - Volume 1" document, even though it is still a bit odd. diff -r c1e9c8102e39 -r bb29b264d9b9 CPU_ROM_KBD.sch --- a/CPU_ROM_KBD.sch Tue Feb 01 00:18:08 2022 +0100 +++ b/CPU_ROM_KBD.sch Sat Feb 12 16:42:18 2022 +0100 @@ -556,7 +556,7 @@ 5900 3800 6600 3800 Wire Wire Line 5900 3900 6600 3900 -Text GLabel 8800 3750 2 50 Input ~ 0 +Text GLabel 8650 3300 2 50 Input ~ 0 ~NMI Text GLabel 6200 4200 2 50 Input ~ 0 ~IRQ @@ -582,7 +582,7 @@ Text GLabel 7500 900 2 50 Output ~ 0 CAPS_LOCK Text Notes 6800 3200 0 50 ~ 0 -Issue 6 boards tend to have\nIC18 (74LS08) fitted for some\nkind of buffering for ~NMI\nand for PHI_OUT.\n\nLK8 is made to enable buffering via IC18 for ~NMI.\nLK9 is made to disable buffering via IC18 for PHI_OUT.\n\nOn such boards, without any links made, buffering\nonly seems to be done for PHI_OUT.\n +Issue 6 boards tend to have\nIC18 (74LS08) fitted for some\nkind of buffering for ~NMI\nand for PHI_OUT.\n\nLK8 is made to disable buffering via IC18 for ~NMI.\nLK9 is made to disable buffering via IC18 for PHI_OUT.\n\nThese buffers were introduced for the Aberdeen ULA,\nand are superfluous for the Ferranti ULA.\nSee the "Acorn Information - Volume 1" document.\n $Comp L 74xx:74LS08 IC18 U 4 1 61F0E37D @@ -641,7 +641,7 @@ Text GLabel 8100 3600 2 50 Input ~ 0 5V Wire Wire Line - 8500 4000 7600 4000 + 7800 4000 7600 4000 Wire Wire Line 7600 4500 7600 4200 Wire Wire Line @@ -676,7 +676,7 @@ Wire Wire Line 6800 3300 8500 3300 Wire Wire Line - 8500 3300 8500 3500 + 8500 3300 8500 4000 Connection ~ 6800 4100 Wire Wire Line 6800 4100 6900 4100 @@ -740,18 +740,18 @@ Text Label 6600 6100 2 50 ~ 0 D[0..7] $Comp -L Jumper:Jumper_3_Bridged12 LK8 +L Jumper:Jumper_2_Open LK8 U 1 1 622A19C1 -P 8500 3750 -F 0 "LK8" V 8546 3837 50 0000 L CNN -F 1 "Enable buffer" V 8455 3837 50 0000 L CNN -F 2 "" H 8500 3750 50 0001 C CNN -F 3 "~" H 8500 3750 50 0001 C CNN - 1 8500 3750 - 0 -1 1 0 +P 8000 4000 +F 0 "LK8" H 8000 4250 50 0000 C CNN +F 1 "Disable buffer" H 8000 4150 50 0000 C CNN +F 2 "" H 8000 4000 50 0001 C CNN +F 3 "~" H 8000 4000 50 0001 C CNN + 1 8000 4000 + -1 0 0 -1 $EndComp Wire Wire Line - 8800 3750 8650 3750 + 8650 3300 8500 3300 $Comp L power:PWR_FLAG #FLG0108 U 1 1 62024ADF @@ -766,6 +766,11 @@ Connection ~ 4450 5000 Wire Wire Line 4450 5000 4550 5000 +Text Notes 4300 6450 0 50 ~ 0 +Note that KiCad cannot determine whether ~CS\nis driven via LK1, so a power flag is required. +Connection ~ 8500 3300 +Wire Wire Line + 8200 4000 8500 4000 Wire Bus Line 2200 1500 6800 1500 Wire Bus Line @@ -780,6 +785,4 @@ 2100 1600 2100 4200 Wire Bus Line 4400 1600 4400 4500 -Text Notes 4300 6450 0 50 ~ 0 -Note that KiCad cannot determine whether ~CS\nis driven via LK1, so a power flag is required. $EndSCHEMATC