Wed, 16 Apr 2014 02:20:43 -0600
fixed bus error handling for real this time (save registers before every instruction and push the saved registers if a bus error occurs, since the instruction may have changed registers before the bus error, and also stop the instruction immediately with longjmp so it won't change memory after the bus error)
This isn't actually what a real 68k does, but it is a good enough approximation. A real 68k will jump back into the middle of the faulted instruction and resume it from the memory access that faulted as opposed to restarting from the beginning like this CPU emulation does. It would be a lot harder to do that with the way this CPU library is designed. Newer versions of MESS basically do the same thing (they use a newer version of this library).
1 #ifndef _WD279X_H
2 #define _WD279X_H
4 #include <stdbool.h>
5 #include <stddef.h>
6 #include <stdint.h>
7 #include <stdio.h>
9 /// WD279x registers
10 typedef enum {
11 WD2797_REG_STATUS = 0, ///< Status register
12 WD2797_REG_COMMAND = 0, ///< Command register
13 WD2797_REG_TRACK = 1, ///< Track register
14 WD2797_REG_SECTOR = 2, ///< Sector register
15 WD2797_REG_DATA = 3 ///< Data register
16 } WD2797_REG;
18 /// WD279x emulator error codes
19 typedef enum {
20 WD2797_ERR_OK = 0, ///< Operation succeeded
21 WD2797_ERR_BAD_GEOM = -1, ///< Bad geometry, or image file too small
22 WD2797_ERR_NO_MEMORY = -2 ///< Out of memory
23 } WD2797_ERR;
25 typedef struct {
26 // Current track, head and sector
27 int track, head, sector;
28 // Track and sector registers
29 int track_reg, sector_reg;
30 // Geometry of current disc
31 int geom_secsz, geom_spt, geom_heads, geom_tracks;
32 // IRQ status
33 bool irq;
34 // Status of last command
35 uint8_t status;
36 // Last command uses DRQ bit?
37 bool cmd_has_drq;
38 // The last value written to the data register
39 uint8_t data_reg;
40 // Last step direction. -1 for "towards zero", 1 for "away from zero"
41 int last_step_dir;
42 // Data buffer, current DRQ pointer and length
43 uint8_t *data;
44 size_t data_pos, data_len;
45 // Current disc image file
46 FILE *disc_image;
47 // Write protect flag
48 int writeable;
49 // LBA at which to start writing
50 int write_pos;
51 // True if a format command is in progress
52 int formatting;
53 } WD2797_CTX;
55 /**
56 * @brief Initialise a WD2797 context.
57 * @param ctx WD2797 context.
58 *
59 * This must be run once when the context is created.
60 */
61 void wd2797_init(WD2797_CTX *ctx);
63 /**
64 * @brief Reset a WD2797 context.
65 * @param ctx WD2797 context.
66 *
67 * This should be run if the WD2797 needs to be reset (nRST line toggled).
68 */
69 void wd2797_reset(WD2797_CTX *ctx);
71 /**
72 * Deinitialise a WD2797 context.
73 * @param ctx WD2797 context.
74 */
75 void wd2797_done(WD2797_CTX *ctx);
77 /**
78 * @brief Read IRQ Rising Edge status. Clears Rising Edge status if it is set.
79 * @note No more IRQs will be sent until the Status Register is read, or a new command is written to the CR.
80 * @param ctx WD2797 context.
81 */
82 bool wd2797_get_irq(WD2797_CTX *ctx);
84 /**
85 * @brief Read DRQ status.
86 * @param ctx WD2797 context.
87 */
88 bool wd2797_get_drq(WD2797_CTX *ctx);
90 /**
91 * @brief Assign a disc image to the WD2797.
92 * @param ctx WD2797 context.
93 * @param fp Disc image file, already opened in "r+b" mode.
94 * @param secsz Sector size: either 128, 256, 512 or 1024.
95 * @param spt Sectors per track.
96 * @param heads Number of heads (1 or 2).
97 * @return Error code; WD279X_E_OK if everything worked OK.
98 */
99 WD2797_ERR wd2797_load(WD2797_CTX *ctx, FILE *fp, int secsz, int spt, int heads, int writeable);
101 /**
102 * @brief Deassign the current image file.
103 * @param ctx WD2797 context.
104 */
105 void wd2797_unload(WD2797_CTX *ctx);
107 /**
108 * @brief Read WD279x register.
109 * @param ctx WD2797 context
110 * @param addr Register address (0, 1, 2 or 3)
111 */
112 uint8_t wd2797_read_reg(WD2797_CTX *ctx, uint8_t addr);
114 /**
115 * @brief Write WD279X register
116 * @param ctx WD2797 context
117 * @param addr Register address (0, 1, 2 or 3)
118 * @param val Value to write
119 */
120 void wd2797_write_reg(WD2797_CTX *ctx, uint8_t addr, uint8_t val);
122 void wd2797_dma_miss(WD2797_CTX *ctx);
123 #endif