nmc93cxx: Rewrite the nmc93cxx emulation

This patch rewrites the nmc93cxx emulation code.
The primary aim of the rewrite is to fix the Qlogic 1080 BIOS v1.11 flashing feature
(the card utilizes a 93C56 chip in 128x16 mode).

This work is derived from the MAME serial EEPROM emulation code
written by Aaron Giles and published under BSD-3-Clause license.
https://github.com/mamedev/mame/blob/master/src/devices/machine/eepromser.cpp

The code is modelled on the MAME code with the following differences:
- Removed support for the ER5911 and MSM16911 EEPROM devices.
- Removed support for the X24C44 NOVRAM device.
- Removed support for the Seiko S-29X90 EEPROM devices.

The 86Box changes:
- The nmc93cxx code now also supports EEPROM devices in 8-bit mode.
- Make the default_content parameter optional.
- Make the nmc93cxx_eeprom_data function to return a const pointer.

src/include/86box/nmc93cxx.h

@@ -1,25 +1,72 @@
-#include <86box/vid_ati_eeprom.h>
+/*
+ * 86Box    A hypervisor and IBM PC system emulator that specializes in
+ *          running old operating systems and software designed for IBM
+ *          PC systems and compatibles from 1981 through fairly recent
+ *          system designs based on the PCI bus.
+ *
+ *          This file is part of the 86Box distribution.
+ *
+ *          Header of the emulation of the National Semiconductors NMC93Cxx EEPROMs
+ *          (16 bits or 8 bits).
+ *
+ * Authors: Cacodemon345
+ *
+ *          Copyright 2023 Cacodemon345
+ */
+#pragma once
 
-typedef struct nmc93cxx_eeprom_t {
-    ati_eeprom_t dev;
-    uint8_t      addrbits;
-    uint16_t     size;
-    char         filename[1024];
-} nmc93cxx_eeprom_t;
+/* Forward declaration to hide internal device state from users. */
+typedef struct nmc93cxx_eeprom_t nmc93cxx_eeprom_t;
 
+/* EEPROM device type used to specify the size of data array. */
+typedef enum nmc93cxx_eeprom_type {
+    /*
+     * Standard 93CX6 class of 16-bit EEPROMs.
+     *
+     * Type / Bits per cell / Number of cells
+     */
+    NMC_93C06_x16_16,
+    NMC_93C46_x16_64,
+    NMC_93C56_x16_128,
+    NMC_93C57_x16_128,
+    NMC_93C66_x16_256,
+    NMC_93C76_x16_512,
+    NMC_93C86_x16_1024,
+
+   /*
+    * Some manufacturers use pin 6 as an "ORG" pin which,
+    * when pulled low, configures memory for 8-bit accesses.
+    *
+    * Type / Bits per cell / Number of cells
+    */
+    NMC_93C46_x8_128,
+    NMC_93C56_x8_256,
+    NMC_93C57_x8_256,
+    NMC_93C66_x8_512,
+    NMC_93C76_x8_1024,
+    NMC_93C86_x8_2048,
+} nmc93cxx_eeprom_type;
+
+/* EEPROM device parameters. */
 typedef struct nmc93cxx_eeprom_params_t {
-    uint16_t  nwords;
-    char     *filename;
-    uint16_t *default_content;
+    /* Device type */
+    nmc93cxx_eeprom_type type;
+    /* Name of EEPROM image file */
+    const char *filename;
+    /*
+     * Optional pointer to the default data buffer.
+     * The buffer size should match the size of EEPROM data array specified by nmc93cxx_eeprom_type.
+     */
+    const void *default_content;
 } nmc93cxx_eeprom_params_t;
 
-/* Read from the EEPROM. */
-uint16_t nmc93cxx_eeprom_read(nmc93cxx_eeprom_t *eeprom);
+/* Read the state of the data output (DO) line. */
+bool nmc93cxx_eeprom_read(nmc93cxx_eeprom_t *dev);
 
-/* Write to the EEPROM. */
-void nmc93cxx_eeprom_write(nmc93cxx_eeprom_t *eeprom, int eecs, int eesk, int eedi);
+/* Set the state of the input lines. */
+void nmc93cxx_eeprom_write(nmc93cxx_eeprom_t *dev, bool eecs, bool eesk, bool eedi);
 
-/* Get EEPROM data array. */
-uint16_t *nmc93cxx_eeprom_data(nmc93cxx_eeprom_t *eeprom);
+/* Returns pointer to the current EEPROM data array. */
+const uint16_t *nmc93cxx_eeprom_data(nmc93cxx_eeprom_t *dev);
 
 extern const device_t nmc93cxx_device;