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The Apple ][ Mainboard ~~~~~~~~~~~~~~~~~~~~~~ This text describes the Apple ][ and ][+ mainboards. These were manufactured from 1974-1984. Since 1984, the Apple ][+ is replaced with the Apple //e, which has a totally new designed mainboard. But some of the topics are valid for the Apple //e too (cassette, game port, slots). 1. Differnces between mainboards ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There are several revisions of the Apple ][ mainboard: Revision number Part number ----------------------------------------------------------------- Rev. 0 820-0001-00 Rev. 1 - Rev. 6 820-0001-0X where X is 1 to 6 Rev. 7 and higher 820-0001-XX where XX is 07 and higher RFI 820-0044-01, 820-0044-C and 820-0044-D The Rev. 0 board does only have 4 hires colors. Rev. 1 to 6 don't have great differences. They have ram-jumpers to configure ram with 4kbit and 16kbit chips. Rev. 7 is a new design and doesn't have the ram-jumpers. It can only use 16kBit chips. The character generator has changed too. The RFI boards were Apple Inc.'s attempt to reduce the radio interference generated by the Apple. These machines have a newly designed case too. The part number can be found at the left border of the board or under the 6502 CPU. 2. Connectors ~~~~~~~~~~~~~ 2.1. Cassette ~~~~~~~~~~~~~ Two earphone-jacks at the rear of the main board are labelled CASS IN and CASS OUT. Older (and simple) cassette recorders work better. With a tape deck, you need to reduce bass, raise tremble and loudness (often ridiculously). $C060: read cassette in $C020: toggle cassette out 2.2. Composite Video Out ~~~~~~~~~~~~~~~~~~~~~~~~ Beside the Cassette jacks is a third jack for the monitor. It provides a normal FBAS signal for NTSC monitors. On the mainboard, just below the monitor jack, is a 4 pin auxilary connector: pin 1 +12V pin 2 -5V pin 3 video out pin 4 GND Below the auxilary video connector is the auxilary video pin and below this pin is the video level adjust. 2.3. Keyboard connector ~~~~~~~~~~~~~~~~~~~~~~~ At the front of the mainboard, right in the middle, besides the bigger 24pin character rom is a empty 16 pin socket. A flat ribbon cable goes from there to the keyboard. +-----_-----+ +5V ! 1 16 ! NC STROBE ! 2 15 ! -12V RESET ! 3 14 ! NC NC ! 4 13 ! D1 D5 ! 5 12 ! D0 D4 ! 6 11 ! D3 D6 ! 7 10 ! D2 GND ! 8 9 ! NC +-----------+ A character is transfered from the keyboard to the Apple ][ by giving the ascii representation of the character on D0-D6 and raising the strobe from low to high for at least 1 us. A character is read from $C000. It is a valid character, if the high bit is set. The high bit is cleared (until STROBE indicates the next keypress), if $C010 is accessed. 2.4. Game connector ~~~~~~~~~~~~~~~~~~~ In the upper right corner, just below the earphone jacks is a second empty 16 pin socket. It is usually used for the paddles or a joystick. But it can more! It has 4 TTL outputs, 1 TTL strobe, 3 TTL inputs and 4 paddle inputs. +-----_-----+ +5V ! 1 16 ! NC SW0 ! 2 15 ! AN0 SW1 ! 3 14 ! AN1 SW2 ! 4 13 ! AN2 STB ! 5 12 ! AN3 PDL0 ! 6 11 ! PDL3 PDL2 ! 7 10 ! PDL1 GND ! 8 9 ! NC +-----------+ STB is a strobe. It goes low for 489 ns, if $C040 is accessed. The annunciators (An0-AN3) are TTL outputs. they are switched by: $C058 AN0 off $C059 AN0 on $C05A AN1 off $C05B AN1 on $C05C AN2 off $C05D AN2 on $C05E AN3 off $C05F AN3 on SW0-SW2 can be read from the high bit of the locations $C061, $C062 and $C063. $C060 is used for the cassette input. The paddles should be read via the monitor routine and not directly. The mechanism is as follows: If $C070 is accessed, four condensators are charged with +5V. They uncharge thru the resistors in the paddles. If the charge drops below a certain value (+1.5V), the high bit of the paddle location goes from low to high. This time can be varied by trimming the resistor (turning the paddle knob). $C064 pdl0 $C065 pdl1 $C066 pdl2 $C067 pdl3 2.5. Slot connector ~~~~~~~~~~~~~~~~~~~ The Apple ][ has eight 50 pin slots near the rear of the main board. These are numbered from 0 to 7 from left to right. The following cards can usually be found in these slots: Slot 0 16kB Language card*, APPLESOFT or Integer ROM card Slot 1 Parallel printer card*, Serial card (conn. with the printer*) Slot 2 Serial Card (connected with a modem*) Slot 3 80 Column card*, Serial Card (connected with a terminal*) Slot 4 RAM card (for example Saturn), Z80 Softcard Slot 5 RAM card, Z80 Softcard, Disk ][ controller card* Slot 6 Disk ][ Controller card* Slot 7 RGB card, hard disk controller card, Z80 Softcard, Clock card This assignment can be varied, but CP/M and UCSD-Pascal assume the cards marked with an asterik in these slots. +-----------+ GND ! 26 25 ! +5V DMA IN ! 27 24 ! DMA OUT INT IN ! 28 23 ! INT OUT NMI ! 29 22 ! DMA IRQ ! 30 21 ! RDY RES ! 31 20 ! I/O STB INH ! 32 19 ! SYNC -12V ! 33 18 ! R/W -5V ! 34 17 ! A15 COL.REF ! 35 16 ! A14 7M ! 36 15 ! A13 Q3 ! 37 14 ! A12 Phi1 ! 38 13 ! A11 USER1 ! 39 12 ! A10 Phi0 ! 40 11 ! A9 DEV.SEL ! 41 10 ! A8 D7 ! 42 9 ! A7 D6 ! 43 8 ! A6 D5 ! 44 7 ! A5 D4 ! 45 6 ! A4 D3 ! 46 5 ! A3 D2 ! 47 4 ! A2 D1 ! 48 3 ! A1 D0 ! 49 2 ! A0 +12V ! 50 1 ! I/O SEL +-----------+ I/O SEL active low, if $CNXX is accessed (N: slotnumber). A0-A15 address bus R/W high read, low write SYNC video sync signal (slot 7 only) I/O STB active low, if $C800-$CFFF is accessed. RDY inserts wait-states INT OUT daisy chained interrupt out DMA OUT daisy chained dma out +5V max. 500mA GND common ground DMA IN daisy chained dma in INT IN daisy chained interrupt in NMI active low non maskerable interrupt IRQ active low maskerable interrupt RESET active low reset INH active low disables rom ($D000-$FFFF) -12V max. 50mA -5V max. 50mA COL.REF 3.5 MHz color reference (slot 7 only) 7M 7 MHz clock Q3 2 MHz clock Phi1 1 MHz clock USER1 active low disables $C000-$C7FF (jumper) Phi0 1 MHz clock (complement of Phi1) DEV.SEL active low, if $C0X0-$C0XF is accessed (X: slotnumber+8) D0-D7 data bus +12V max. 250mA