diff options
| author | Michael Pavone <pavone@retrodev.com> | 2014-02-03 09:18:10 -0800 |
|---|---|---|
| committer | Michael Pavone <pavone@retrodev.com> | 2014-02-03 09:18:10 -0800 |
| commit | e14e901df89aa1823b1479366b58196247c16bd2 (patch) | |
| tree | 14e076b4b2a409974b73dd15278c8394833ad89c /zruntime.S | |
| parent | efcdc09b1c58be04a53fa84ea34981d4231c1a78 (diff) | |
Initial attempt at emulating extended bank area access delays when 68K bus is busy with VDP stuff. Also emulate the extra delay on the second access of a word-wide read to the bank area. Needs work as it seems to break stuff.
Diffstat (limited to 'zruntime.S')
| -rw-r--r-- | zruntime.S | 65 |
1 files changed, 64 insertions, 1 deletions
@@ -34,6 +34,21 @@ sync_io: pop %rbx ret /* return to caller of z80_run */ +forced_sync: + movw $0, 164(%rsi) + call z80_save_context_scratch + pop %rax /*return address in read/write func*/ + pop 104(%rsi) /*return address in native code*/ + mov %rax, (%rsi) + + pop %r15 /* restore callee saved regsiters */ + pop %r14 + pop %r13 + pop %r12 + pop %rbp + pop %rbx + ret /* return to caller of z80_run */ + .global z80_handle_cycle_limit_int z80_handle_cycle_limit_int: cmp 116(%rsi), %ebp @@ -107,8 +122,14 @@ z80_read_ram: mov (%r11, %r13), %r13b ret z80_read_bank: - /* approximation of wait states for 68K bus access */ + push %rsi + mov 144(%rsi), %rsi /* get system context pointer */ + cmp $0, 120(%rsi) /* check bus busy flag */ + pop %rsi + jne bus_busy + /* approximation of wait states for normal 68K bus access */ add $3, %ebp +z80_read_bank_cont: and $0x7FFF, %r13 cmp $0, %r12 je slow_bank_read @@ -119,6 +140,10 @@ z80_read_bank: slow_bank_read: /* TODO: Call into C to implement this */ ret +bus_busy: + mov %edi, %ebp + call forced_sync + jp z80_read_bank_cont z80_read_ym2612: call z80_save_context mov %r13w, %di @@ -199,6 +224,8 @@ z80_write_vdp: .global z80_read_word z80_read_word: call z_inccycles + cmp $0x8000, %r13w + jae z80_read_bank_word push %r13 call z80_read_byte_noinc mov %r13b, %r14b @@ -210,6 +237,42 @@ z80_read_word: mov %r14b, %r13b ret +z80_read_bank_word: + push %rsi + mov 144(%rsi), %rsi /* get system context pointer */ + cmp $0, 120(%rsi) /* check bus busy flag */ + pop %rsi + jne bus_busy_word + add $3, %ebp /* first read typically has 3 wait states */ +z80_read_bank_word_cont: + push %r13 + call z80_read_bank_cont + mov %r13b, %r14b + pop %r13 + inc %r13 + call z_inccycles + push %rsi + mov 144(%rsi), %rsi /* get system context pointer */ + cmp $0, 120(%rsi) /* check bus busy flag */ + pop %rsi + jne bus_busy_word2 + add $4, %ebp /* second read typically has 4 wait states */ +z80_read_bank_word_cont2: + call z80_read_bank_cont + shl $8, %r13w + mov %r14b, %r13b + ret + +bus_busy_word: + mov %edi, %ebp + call forced_sync + jp z80_read_bank_word_cont + +bus_busy_word2: + mov %edi, %ebp + call forced_sync + jp z80_read_bank_word_cont2 + .global z80_write_word_highfirst z80_write_word_highfirst: call z_inccycles |