mirror of
https://github.com/ivanizag/izapple2.git
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142 lines
4.1 KiB
Go
142 lines
4.1 KiB
Go
package izapple2
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/*
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Swyft card for Apple IIe
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See:
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https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Other/IAI%20SwyftCard/
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*/
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/*
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"SwyftCard Hardware Theory of Operation". SwyftCard manual, page 98:
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The SwyftCard is a plug-in card for the Apple /Ie that operates in
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slot 3. The card contains three integrated circuits which provide a
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power-on reset circuit, storage for the SwyftCard program, and control
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signals for the card. The card operates by asserting the Apple IIe bus
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signal INH' which disables the built-in ROM and enables the SwyftCard
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ROM. This permits the SwyftCard program to take over the system at
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power-on and run the SwyftCard program. (Please refer to the
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schematic.)
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The LM311 voltage comparator is connected to provide the power-on
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reset function. When the Apple lIe is first turned on, the power-on
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reset circuit resets the PAL, turning on the SwyftCard and disabling
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the Apple IIe internal ROM. The power-on reset circuit must be
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provided because the existing Apple IIe reset function is used by
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many Apple lie programs for a "warm start": if Apple lie reset always
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started the SwyftCard, other programs could not use the "warm start."
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The 27128 PROM is used to store the SwyftCard program. The PROM
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contains 16384 bytes which are mapped into the address space
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$DOOO - $FFFF. Since the address space is only 12 Kbytes, there are
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two 4 Kbyte sections of the PROM mapped into the address space
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$DOOO-$DFFF.
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The card is controlled by the PAL. When the SwyftCard is active, the
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PAL asserts the INH' signal, enables the PROM, and bank switches
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the $DOOO-$DFFF address space. The card is controlled by two soft
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switches. The soft switches are controlled by accessing the following
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memory locations with either a read or a write operation.
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$COBO - SwyftCard active, Bank 1
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$COB1 - SwyftCard inactive, Bank 1
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$COB2 - SwyftCard active, Bank 2
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When the power-on reset circuit asserts the RES signal on Pin 3 of the
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PAL, the SwyftCard is made active in Bank 1. Accessing location
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$COB1 deactivates the SwyftCard for normal Apple IIe operation.
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The INH' line is driven by a tri-state driver, so if another card in the
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Apple /Ie asserts the IINH' signal there will not be a bus contention.
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However, there will be a bus contention on the data bus if another card
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attempts to control the bus while the SwyftCard is active.
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The Cx00 rom is not used. The card is expected to be installed in
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slot 3 of an Apple IIe with the 80 column firmware already present.
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*/
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// CardSwyft represents a Swyft card
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type CardSwyft struct {
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cardBase
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bank2 bool
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rom []uint8
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}
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func newCardSwyftBuilder() *cardBuilder {
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return &cardBuilder{
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name: "SwyftCard",
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description: "Card with the ROM needed to run the Swyftcard word processing system",
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requiresIIe: true,
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buildFunc: func(params map[string]string) (Card, error) {
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var c CardSwyft
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// Load main ROM replacement
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data, _, err := LoadResource("<internal>/SwyftCard ROM.bin")
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if err != nil {
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return nil, err
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}
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c.rom = data
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return &c, nil
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},
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}
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}
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func (c *CardSwyft) assign(a *Apple2, slot int) {
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if slot != 3 {
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panic("SwyftCard must be installed in slot 3")
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}
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c.addCardSoftSwitchRW(0, func() uint8 {
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a.mmu.inhibitROM(c)
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c.bank2 = false
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return 0x55
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}, "SWYFTONBANK1")
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c.addCardSoftSwitchRW(1, func() uint8 {
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a.mmu.inhibitROM(nil)
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c.bank2 = false
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return 0x55
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}, "SWYFTOFFBANK1")
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c.addCardSoftSwitchRW(2, func() uint8 {
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a.mmu.inhibitROM(c)
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c.bank2 = true
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return 0x55
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}, "SWYFTONBANK2")
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c.cardBase.assign(a, slot)
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a.mmu.inhibitROM(c)
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}
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func (c *CardSwyft) translateAddress(address uint16) uint16 {
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/*
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The four 4k sections of the 16k ROM image are mapped:
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D000-DFFF (page 1)
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D000-DFFF (page 2)
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E000-EFFF
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F000-FFFF
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*/
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if address >= 0xE000 {
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return address - 0xE000 + 0x2000
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}
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if !c.bank2 {
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return address - 0xD000
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}
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return address - 0xD000 + 0x1000
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}
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func (c *CardSwyft) peek(address uint16) uint8 {
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return c.rom[c.translateAddress(address)]
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}
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func (c *CardSwyft) poke(address uint16, value uint8) {
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// Nothing
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}
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func (c *CardSwyft) setBase(base uint16) {
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// Nothing
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}
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