From 8a91051e25b958c5d2111aa231d17411a6c9694f Mon Sep 17 00:00:00 2001
From: SarahW <pcem@pcem-emulator.co.uk>
Date: Mon, 1 Apr 2019 21:38:21 +0100
Subject: [PATCH] SST flash now keeps local copy of flash data to write back on
 device close. Prevents flash corruption when switching models and PCem loads
 the new BIOS before writing out the old flash.

---
 src/sst39sf010.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/sst39sf010.c b/src/sst39sf010.c
index 57969b4..8acb664 100644
--- a/src/sst39sf010.c
+++ b/src/sst39sf010.c
@@ -12,6 +12,7 @@ typedef struct sst_t
         int dirty;
         
         char flash_path[1024];
+        uint8_t data[0x20000];
 } sst_t;
 
 #define SST_CHIP_ERASE    0x10
@@ -30,7 +31,10 @@ static void sst_new_command(sst_t *sst, uint8_t val)
         {
                 case SST_CHIP_ERASE:
                 if (sst->erase)
+                {
                         memset(rom, 0xff, 0x20000);
+                        memset(sst->data, 0xff, 0x20000);
+                }
                 sst->command_state = 0;
                 sst->erase = 0;
                 break;
@@ -69,6 +73,7 @@ static void sst_sector_erase(sst_t *sst, uint32_t addr)
 {
 //        pclog("SST sector erase %08x\n", addr);
         memset(&rom[addr & 0x1f000], 0xff, 4096);
+        memset(&sst->data[addr & 0x1f000], 0xff, 4096);
         sst->dirty = 1;
 }
 
@@ -121,6 +126,7 @@ static void sst_write(uint32_t addr, uint8_t val, void *p)
                 case 3:
 //                pclog("Byte program %08x %02x\n", addr, val);
                 rom[addr & 0x1ffff] = val;
+                sst->data[addr & 0x1ffff] = val;
                 sst->command_state = 0;
                 sst->dirty = 1;
                 break;
@@ -184,6 +190,7 @@ static void *sst_39sf010_init()
                 fread(rom, 0x20000, 1, f);
                 fclose(f);
         }
+        memcpy(sst->data, rom, 0x20000);
 
         clear_id_mode(sst);
 	
@@ -197,7 +204,7 @@ static void sst_39sf010_close(void *p)
         if (sst->dirty)
         {
                 FILE *f = romfopen(sst->flash_path, "wb");
-                fwrite(rom, 0x20000, 1, f);
+                fwrite(sst->data, 0x20000, 1, f);
                 fclose(f);
         }