mirror of https://github.com/pevans/erc-c.git
303 lines
8.4 KiB
C
303 lines
8.4 KiB
C
/*
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* apple2.dbuf.c
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*
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* Handle reads and writes to our display buffers and the soft switches
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* that manage them. There are a number of conditions which may cause
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* our I/O to use the auxiliary memory segment instead of the main one;
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* additionally, we can signal to the VM that we need to redraw stuff
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* when writes do happen.
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*/
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#include "apple2/dbuf.h"
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#include "apple2/draw.h"
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#include "vm_reflect.h"
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static size_t switch_reads[] = {
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0xC01A,
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0xC01B,
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0xC01E,
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0xC01F,
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0xC050,
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0xC051,
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0xC052,
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0xC053,
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0xC05E,
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0xC05F,
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0xC07E,
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0xC07F,
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};
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static size_t switch_writes[] = {
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0xC00C,
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0xC00D,
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0xC00E,
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0xC00F,
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0xC050,
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0xC051,
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0xC052,
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0xC053,
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0xC05E,
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0xC05F,
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0xC07E,
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0xC07F,
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};
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/*
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* Handle reads from text page 1 and hires graphics page 1 (the display
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* buffers).
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*/
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SEGMENT_READER(apple2_dbuf_read)
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{
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apple2 *mach = (apple2 *)_mach;
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// When 80STORE is high, we are allowed to look into two other flags
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// to see if they are set and modify our behavior accordingly.
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if (mach->memory_mode & MEMORY_80STORE) {
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// If the address is contained within text page 1, then we need
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// to look up memory in aux. (Uh, don't ask why we switch page 1
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// with the PAGE2 flag.) Otherwise, if the address is contained
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// in hires graphics page 1, then that must also use aux memory
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// if _both_ the PAGE2 and HIRES bits are set.
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if (addr >= 0x400 && addr < 0x800 &&
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(mach->memory_mode & MEMORY_PAGE2)
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) {
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segment = mach->aux;
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} else if (addr >= 0x2000 && addr < 0x4000 &&
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(mach->memory_mode & MEMORY_PAGE2) &&
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(mach->memory_mode & MEMORY_HIRES)
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) {
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segment = mach->aux;
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}
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}
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// In all other cases, we _must_ use the segment that was passed in.
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// That segment may be aux memory if MEMORY_READ_AUX is set, and if
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// so, that would be the desired behavior.
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return segment->memory[addr];
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}
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/*
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* Many of the cautions and notes in the apple2_dbuf_read function
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* apply here as well.
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*/
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SEGMENT_WRITER(apple2_dbuf_write)
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{
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apple2 *mach = (apple2 *)_mach;
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if (mach->memory_mode & MEMORY_80STORE) {
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if (addr >= 0x400 && addr < 0x800 &&
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(mach->memory_mode & MEMORY_PAGE2)
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) {
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segment = mach->aux;
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} else if (addr >= 0x2000 && addr < 0x4000 &&
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(mach->memory_mode & MEMORY_PAGE2) &&
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(mach->memory_mode & MEMORY_HIRES)
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) {
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segment = mach->aux;
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}
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}
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// Again, segment is allowed to be that which was passed in if
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// 80STORE is low.
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segment->memory[addr] = value;
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apple2_notify_refresh(mach);
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}
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/*
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* Map the text page 1 and hires graphics page 1 addresses to the dbuf
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* read and write functions.
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*/
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void
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apple2_dbuf_map(vm_segment *segment)
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{
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size_t addr;
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int i, rlen, wlen;
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for (addr = 0x400; addr < 0x800; addr++) {
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vm_segment_read_map(segment, addr, apple2_dbuf_read);
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vm_segment_write_map(segment, addr, apple2_dbuf_write);
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}
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for (addr = 0x2000; addr < 0x4000; addr++) {
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vm_segment_read_map(segment, addr, apple2_dbuf_read);
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vm_segment_write_map(segment, addr, apple2_dbuf_write);
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}
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rlen = sizeof(switch_reads) / sizeof(size_t);
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wlen = sizeof(switch_writes) / sizeof(size_t);
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for (i = 0; i < rlen; i++) {
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vm_segment_read_map(segment, switch_reads[i], apple2_dbuf_switch_read);
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}
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for (i = 0; i < wlen; i++) {
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vm_segment_write_map(segment, switch_writes[i], apple2_dbuf_switch_write);
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}
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}
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/*
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* Handle all read switches for display buffer code. Some switches
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* respond to either reads _or_ writes, so you may see some cases
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* duplicated in the write map.
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*
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* Additionally, a number of the display modes also count as memory
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* modes, and are handled in apple2.mem.c. Notably, some are HIRES,
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* PAGE2, and 80STORE.
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*/
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SEGMENT_READER(apple2_dbuf_switch_read)
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{
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apple2 *mach = (apple2 *)_mach;
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switch (addr) {
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case 0xC01E:
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return mach->display_mode & DISPLAY_ALTCHAR
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? 0x80
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: 0x00;
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case 0xC01F:
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return mach->display_mode & DISPLAY_80COL
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? 0x80
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: 0x00;
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case 0xC01A:
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return mach->display_mode & DISPLAY_TEXT
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? 0x80
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: 0x00;
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case 0xC01B:
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return mach->display_mode & DISPLAY_MIXED
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? 0x80
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: 0x00;
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// NOTE: IOUDIS is the only bit that seems to share a write
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// address with a read address. We can certainly handle that,
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// since we support separate read and write tables! But it's
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// interesting that they chose to do that, where they mostly
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// stick with separate addresses for separate functions.
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case 0xC07E:
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return mach->display_mode & DISPLAY_IOUDIS
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? 0x80
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: 0x00;
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case 0xC07F:
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return mach->display_mode & DISPLAY_DHIRES
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? 0x80
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: 0x00;
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// As in apple2.mem.c, the following switch cases are duplicated
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// from the switch_write function because the Apple II expects
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// both reads and writes to have the same effect at these
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// addresses.
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case 0xC050:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_TEXT);
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return 0x00;
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case 0xC051:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_TEXT);
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return 0x80;
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case 0xC052:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_MIXED);
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return 0x00;
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case 0xC053:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_MIXED);
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return 0x80;
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case 0xC05E:
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if (mach->display_mode & DISPLAY_IOUDIS) {
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_DHIRES);
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return 0x80;
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}
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return 0x00;
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case 0xC05F:
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if (mach->display_mode & DISPLAY_IOUDIS) {
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_DHIRES);
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return 0x80;
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}
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return 0x00;
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}
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// ???
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return 0x00;
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}
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/*
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* Here we update the statuses of the various display soft switches,
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* and--there's a bunch of them!
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*/
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SEGMENT_WRITER(apple2_dbuf_switch_write)
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{
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apple2 *mach = (apple2 *)_mach;
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switch (addr) {
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case 0xC00E:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_ALTCHAR);
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break;
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case 0xC00F:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_ALTCHAR);
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break;
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case 0xC00C:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_80COL);
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break;
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case 0xC00D:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_80COL);
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break;
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case 0xC050:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_TEXT);
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break;
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case 0xC051:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_TEXT);
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break;
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case 0xC052:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_MIXED);
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break;
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case 0xC053:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_MIXED);
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break;
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case 0xC07E:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_IOUDIS);
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break;
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case 0xC07F:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_IOUDIS);
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break;
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case 0xC05E:
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apple2_set_display(mach,
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mach->display_mode | DISPLAY_DHIRES);
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break;
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case 0xC05F:
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apple2_set_display(mach,
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mach->display_mode & ~DISPLAY_DHIRES);
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break;
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}
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}
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