From 631085f1e6fcab094e87ef691f15b299781017af Mon Sep 17 00:00:00 2001
From: Luke Usher <luke@usher.cc>
Date: Mon, 14 Aug 2023 21:16:43 +0100
Subject: [PATCH] ps1: separate /ack and transfer delays into two counters

---
 ares/ps1/peripheral/io.cpp            | 16 +++++-----------
 ares/ps1/peripheral/peripheral.cpp    | 17 ++++++++++++-----
 ares/ps1/peripheral/peripheral.hpp    |  3 ++-
 ares/ps1/peripheral/serialization.cpp |  3 ++-
 ares/ps1/system/serialization.cpp     |  2 +-
 5 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/ares/ps1/peripheral/io.cpp b/ares/ps1/peripheral/io.cpp
index 859a71ad7e..0eea3afedd 100644
--- a/ares/ps1/peripheral/io.cpp
+++ b/ares/ps1/peripheral/io.cpp
@@ -13,36 +13,30 @@ auto Peripheral::transmit(u8 data) -> void {
 
   //Calculate the number of cycles required to transfer a byte at the current baud rate
   //This is added to the /ACK delay to determine the total duration until /ACK is asserted
-  //NOTE: transfer time is only emulated for memory cards for now, not controllers
-  //enabling it for controllers causes games to drop input; needs further investigation
   u8 factors[4] = {1, 1, 16, 64};
-  auto transferCycles = ((io.baudrateReloadValue * factors[io.baudrateReloadFactor])) * 8;
+  io.transferCounter = ((io.baudrateReloadValue * factors[io.baudrateReloadFactor])) * 8;
 
   if(io.slotNumber == 0) {
     if(!memoryCardPort1.active()) {
-      io.receiveSize = 1;
       io.receiveData = controllerPort1.bus(data);
-      if(controllerPort1.acknowledge()) io.counter = /*transferCycles*/ + 338; // approx 9.98us
+      if(controllerPort1.acknowledge()) io.ackCounter = 338; // approx 9.98us
     }
 
     if(!controllerPort1.active()) {
-      io.receiveSize = 1;
       io.receiveData = memoryCardPort1.bus(data);
-      if(memoryCardPort1.acknowledge()) io.counter = transferCycles + 170; // approx 5us
+      if(memoryCardPort1.acknowledge()) io.ackCounter = 170; // approx 5us
     }
   }
 
   if(io.slotNumber == 1) {
     if(!memoryCardPort2.active()) {
-      io.receiveSize = 1;
       io.receiveData = controllerPort2.bus(data);
-      if(controllerPort2.acknowledge()) io.counter = /*transferCycles*/ + 338; // approx 9.98us
+      if(controllerPort2.acknowledge()) io.ackCounter = 338; // approx 9.98us
     }
 
     if(!controllerPort2.active()) {
-      io.receiveSize = 1;
       io.receiveData = memoryCardPort2.bus(data);
-      if(memoryCardPort2.acknowledge()) io.counter = transferCycles + 170; // approx 5us
+      if(memoryCardPort2.acknowledge()) io.ackCounter = 170; // approx 5us
     }
   }
 }
diff --git a/ares/ps1/peripheral/peripheral.cpp b/ares/ps1/peripheral/peripheral.cpp
index 937b640772..b5daa750d9 100644
--- a/ares/ps1/peripheral/peripheral.cpp
+++ b/ares/ps1/peripheral/peripheral.cpp
@@ -18,9 +18,16 @@ auto Peripheral::unload() -> void {
 }
 
 auto Peripheral::main() -> void {
-  if(io.counter > 0) {
-    if(--io.counter == 0) {
-      if(!io.acknowledgeAsserted) {
+  if(io.transferCounter > 0) {
+    if(--io.transferCounter == 0) {
+      //transfer complete, set receive size to 1 byte
+      io.receiveSize = 1;
+    }
+  }
+
+  if(io.transferCounter == 0 && io.ackCounter > 0) {
+    if(--io.ackCounter == 0) {
+      if (!io.acknowledgeAsserted) {
         //Assert /ACK and fire the IRQ
         io.interruptRequest = 1;
         io.acknowledgeAsserted = 1;
@@ -28,9 +35,9 @@ auto Peripheral::main() -> void {
           interrupt.raise(Interrupt::Peripheral);
         }
 
-        io.counter = 96; // ACK duration is approx 96 cycles (2.84us)
+        io.ackCounter = 96; // ACK duration is approx 96 cycles (2.84us)
       } else {
-        //Deassert /ACK
+        //De-assert /ACK
         io.acknowledgeAsserted = 0;
       }
     }
diff --git a/ares/ps1/peripheral/peripheral.hpp b/ares/ps1/peripheral/peripheral.hpp
index e06beda36e..d38f2f0ff9 100644
--- a/ares/ps1/peripheral/peripheral.hpp
+++ b/ares/ps1/peripheral/peripheral.hpp
@@ -77,7 +77,8 @@ struct Peripheral : Thread, Memory::Interface {
     n16 baudrateReloadValue;
 
     //internal
-    i32 counter;
+    i32 transferCounter;
+    i32 ackCounter;
   } io;
 };
 
diff --git a/ares/ps1/peripheral/serialization.cpp b/ares/ps1/peripheral/serialization.cpp
index 4cd40c3731..576a1af50a 100644
--- a/ares/ps1/peripheral/serialization.cpp
+++ b/ares/ps1/peripheral/serialization.cpp
@@ -31,5 +31,6 @@ auto Peripheral::serialize(serializer& s) -> void {
   s(io.slotNumber);
   s(io.unknownCtrl_14_15);
   s(io.baudrateReloadValue);
-  s(io.counter);
+  s(io.transferCounter);
+  s(io.ackCounter);
 }
diff --git a/ares/ps1/system/serialization.cpp b/ares/ps1/system/serialization.cpp
index 88d21df566..f51606f8b0 100644
--- a/ares/ps1/system/serialization.cpp
+++ b/ares/ps1/system/serialization.cpp
@@ -1,4 +1,4 @@
-static const string SerializerVersion = "v131";
+static const string SerializerVersion = "v133";
 
 auto System::serialize(bool synchronize) -> serializer {
   serializer s;