From bbb520fd12f58eb330762f73af28482409ec90a8 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 6 Mar 2024 15:31:07 -0500
Subject: [PATCH] Transcribe some notes.
---
Machines/Acorn/Archimedes/Archimedes.cpp | 29 +++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/Machines/Acorn/Archimedes/Archimedes.cpp b/Machines/Acorn/Archimedes/Archimedes.cpp
index b84c923c7..7abf050bf 100644
--- a/Machines/Acorn/Archimedes/Archimedes.cpp
+++ b/Machines/Acorn/Archimedes/Archimedes.cpp
@@ -94,6 +94,7 @@ struct Memory {
high_rom_access_time_ = ROMAccessTime((address >> 6) & 3);
low_rom_access_time_ = ROMAccessTime((address >> 4) & 3);
page_size_ = PageSize((address >> 2) & 3);
+ update_mapping();
logger.info().append("MEMC Control: %08x/%08x -> OS:%d sound:%d video:%d high:%d low:%d size:%d", address, source, os_mode_, sound_dma_enable_, video_dma_enable_, high_rom_access_time_, low_rom_access_time_, page_size_);
@@ -126,7 +127,8 @@ struct Memory {
return true;
case Zone::AddressTranslator:
- logger.error().append("TODO: Write address translator of %08x to %08x", source, address);
+ pages_[address & 0x7f] = address;
+ update_mapping();
break;
default:
@@ -166,6 +168,7 @@ struct Memory {
break;
case Zone::HighROM:
+ // TODO: require A24=A25=0, then A25=1.
has_moved_rom_ = true;
source = high_rom<IntT>(address);
return true;
@@ -198,6 +201,11 @@ struct Memory {
return true;
}
+ Memory() {
+ // Install initial logical memory map.
+ update_mapping();
+ }
+
private:
bool has_moved_rom_ = false;
std::array<uint8_t, 4*1024*1024> ram_{};
@@ -264,11 +272,30 @@ struct Memory {
template <typename IntT, bool is_read>
IntT *logical_ram(uint32_t address, InstructionSet::ARM::Mode) {
+ // TODO: (1) which logical page is this?
logger.error().append("TODO: Logical RAM mapping at %08x", address);
+
+ // 4kb:
+ // A[6:0] -> PPN[6:0]
+ // A[11:10] -> LPN[12:11]; A[22:12] -> LPN[10:0]
+
+ // 8kb:
+ // A[0] -> PPN[6]; A[6:1] -> PPN[5:0]
+ // A[11:10] -> LPN[11:10]; A[22:13] -> LPN[9:0]
+
+ // 16kb:
+ // A[1:0] -> PPN[6:5]; A[6:2] -> PPN[4:0]
+ // A[11:10] -> LPN[10:9]; A[22:14] -> LPN[8:0]
+
+ // 32kb:
+ // A[1] -> PPN[6]; A[2] -> PPN[5]; A[0] -> PPN[4]; A[6:3] -> PPN[6:3]
+ // A[11:10] -> LPN[9:8]; A[22:15] -> LPN[7:0]
+
return nullptr;
}
void update_mapping() {
+ logger.error().append("TODO: Update logical RAM mapping");
}
};