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ns32000: always perform bus-sized writes to aligned memory

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This commit is contained in:
Patrick Mackinlay 2022-07-18 11:18:27 +07:00
parent 6f2d0788c5
commit f4347601a0
2 changed files with 41 additions and 5 deletions
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44
src/devices/cpu/ns32000/ns32000.cpp
View File

@ -340,7 +340,7 @@ template <int Width> template<typename T> T ns32000_device<Width>::mem_read(unsi
return 0;
}
template <int Width> template<typename T> void ns32000_device<Width>::mem_write(unsigned st, u32 address, T data, bool user)
template <int Width> template<typename T> void ns32000_device<Width>::mem_write(unsigned st, u32 address, u64 data, bool user)
{
u32 physical = address;
ns32000_mmu_interface::translate_result tr = m_mmu ?
@ -402,10 +402,44 @@ template <int Width> template<typename T> void ns32000_device<Width>::mem_write(
else
{
// aligned access
/*
* Tektronix 4132 firmware requires that MOVB rN,<mem> (where mem
* is a word-aligned memory address) drives a 16-bit value from the
* register onto the data bus (with /HBE deasserted). The effect is
* important when the data is being written to a fixed-width 16-bit
* register (Am9516 in this case), as the byte enables are ignored
* and a 16-bit value is latched. This code assumes the same effect
* occurs with word/dword-aligned MOVB/MOVW on the 32032 and 32332.
*/
// TODO: verify how real hardware behaves
switch (sizeof(T))
{
case 1: m_bus[st].write_byte(physical, data); break;
case 2: m_bus[st].write_word(physical, data); break;
case 1:
if (Width == 1)
{
unsigned const shift = (physical & 1) * 8;
m_bus[st].write_word(physical, data << shift, 0xffU << shift);
}
else if (Width == 2)
{
unsigned const shift = (physical & 3) * 8;
m_bus[st].write_dword(physical, data << shift, 0xffU << shift);
}
else
m_bus[st].write_byte(physical, data);
break;
case 2:
if (Width == 2)
{
unsigned const shift = (physical & 2) * 8;
m_bus[st].write_dword(physical, data << shift, 0xffffU << shift);
}
else
m_bus[st].write_word(physical, data);
break;
case 4: m_bus[st].write_dword(physical, data); break;
case 8: m_bus[st].write_qword(physical, data); break;
}
@ -1645,7 +1679,9 @@ template <int Width> void ns32000_device<Width>::execute_run()
mode[1].write_i(size);
decode(mode, bytes);
u32 const src = gen_read(mode[0]);
// special-case non-masked source data when moving from
// register to memory; see comments in mem_write()
u32 const src = (mode[0].type == REG) ? m_r[mode[0].gen] : gen_read(mode[0]);
gen_write(mode[1], src);

2
src/devices/cpu/ns32000/ns32000.h
View File

@ -120,7 +120,7 @@ protected:
// memory accessors
template <typename T> T mem_read(unsigned st, u32 address, bool user = false, bool pfs = false);
template <typename T> void mem_write(unsigned st, u32 address, T data, bool user = false);
template <typename T> void mem_write(unsigned st, u32 address, u64 data, bool user = false);
// instruction fetch/decode helpers
template <typename T> T fetch(unsigned &bytes);