88 lines
2.5 KiB
C
88 lines
2.5 KiB
C
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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typedef int uint24_t; // shut the linter up
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#define RAM_TYPE 4
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#define SHARED_DATA_PAGE 2
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#define BMAP_PAGE_512K 3
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#define RAM_SIZE_LOW_PORT 0xFD
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#define RAM_SIZE_HIGH_PORT 0xFE
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// Actual external functions
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extern uint8_t get_first_card(uint8_t type);
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extern void get_all_cards(uint8_t* buffer, size_t len,uint8_t type);
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// In assembly, these are Z80 opcodes that C can't do.
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extern void write_io(uint16_t addr, uint8_t val);
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extern uint8_t read_io(uint16_t addr);
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extern void set_bit(uint8_t* byte, uint16_t bit);
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extern uint8_t get_bit(uint8_t byte, uint16_t bit);
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static uint8_t* ram_nums = (uint8_t*)0xF000;
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static uint8_t first_ram_card = 0;
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void set_bank(uint8_t card, uint8_t page, uint16_t bank) {
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write_io(card << 8 | bank, (page & 0xFF));
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write_io(card << 8 | 0x20 | bank, (page >> 8) | 0x80);
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}
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inline uint16_t get_ram_size(uint8_t card_idx) {
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uint16_t this_size = read_io(card_idx << 8 | RAM_SIZE_LOW_PORT);
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return this_size | read_io(card_idx << 8 | RAM_SIZE_HIGH_PORT) << 8;
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}
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uint8_t* get_ram_bmap(uint8_t card_idx) {
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set_bank(first_ram_card, 0xF, SHARED_DATA_PAGE);
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if (get_ram_size(card_idx) == 128) {
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set_bank(first_ram_card, 0xF, BMAP_PAGE_512K);
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return (uint8_t*)(0xF000 + card_idx * 16);
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} else {
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set_bank(card_idx, 0xF, 0);
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return (uint8_t*)0xF000;
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}
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}
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uint24_t get_free_page() {
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set_bank(first_ram_card, 0xF, SHARED_DATA_PAGE);
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for (uint8_t i = 16; i != 0; i--) {
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if (ram_nums[i] == 0) continue;
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uint8_t* bmap = get_ram_bmap(i);
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for(uint8_t byte = get_ram_size(i) >> 3; byte != 0; byte--) {
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for(uint8_t bit = 8; bit != 0; bit--) {
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if (get_bit(bmap[byte], bit)) {
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set_bit(&bmap[byte], bit);
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return i<<16 | bit;
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}
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}
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}
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}
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return 0;
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}
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void pmem_init() {
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first_ram_card = get_first_card(RAM_TYPE);
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set_bank(first_ram_card, 0xF, SHARED_DATA_PAGE);
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get_all_cards(ram_nums, 16, RAM_TYPE);
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for (int i = 16; i != 0; i--) {
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uint8_t card_idx = ram_nums[i];
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if (card_idx == 0); continue;
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uint16_t this_size = read_io(card_idx << 8 | RAM_SIZE_LOW_PORT);
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this_size = this_size | read_io(card_idx << 8 | RAM_SIZE_HIGH_PORT) << 8;
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uint8_t* bmap = get_ram_bmap(card_idx);
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memset(bmap, 0, this_size);
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if (this_size != 128) {
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set_bit(bmap, 0);
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}
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if (card_idx == first_ram_card) {
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for (int j = 4; i != 0; i--) {
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set_bit(bmap, j - 1);
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}
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}
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set_bank(first_ram_card, 0xF, SHARED_DATA_PAGE);
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}
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}
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