diff --git a/boot.c b/boot.c
index c72e24ed..53aefa8b 100644
--- a/boot.c
+++ b/boot.c
@@ -22,7 +22,7 @@ extern __xdata struct machine_runtime machine_detected;
 extern __xdata uint8_t sfr_data[4];
 extern volatile __xdata uint32_t ticks;
 extern __xdata uint8_t tx_seq;
-extern __code uint8_t * __code hex;
+extern __code const uint8_t * __code const hex;
 
 
 
diff --git a/cmd_parser.c b/cmd_parser.c
index 55bba78b..bfa75b06 100644
--- a/cmd_parser.c
+++ b/cmd_parser.c
@@ -26,15 +26,15 @@
 #pragma codeseg BANK2
 #pragma constseg BANK2
 
-extern __code struct machine machine;
+extern __code const struct machine machine;
 extern __xdata bool stp_enabled;
-extern __code uint8_t log_to_phys_port[9];
+extern __code const uint8_t log_to_phys_port[9];
 
 extern volatile __xdata uint32_t ticks;
 extern volatile __xdata uint8_t sfr_data[4];
 
-extern __code uint8_t * __code greeting;
-extern __code uint8_t * __code hex;
+extern __code const uint8_t * __code const greeting;
+extern __code const uint8_t * __code const hex;
 
 extern __xdata uint8_t flash_buf[FLASH_BUF_SIZE];
 extern __xdata struct flash_region_t flash_region;
@@ -105,7 +105,7 @@ inline uint8_t isnumber(uint8_t l)
 	return (l <= ('9'-'0'));
 }
 
-uint8_t cmd_compare(uint8_t start, __code uint8_t * cmd)
+uint8_t cmd_compare(uint8_t start, __code const uint8_t * cmd)
 {
 	if (cmd_words_len == 0 || start > (cmd_words_len - 1)) {
 		return 0;
diff --git a/httpd/httpd.c b/httpd/httpd.c
index 9e9bd13a..ab61ca7c 100644
--- a/httpd/httpd.c
+++ b/httpd/httpd.c
@@ -22,9 +22,9 @@
 extern volatile __xdata uint8_t sfr_data[4];
 extern volatile __xdata uint32_t ticks;
 extern __xdata uint8_t cmd_capture;	/* owned by rtlplayground.c, see write_char_no_syslog() */
-extern __code uint8_t * __code hex;
-extern __code struct f_data f_data[];
-extern __code char * __code mime_strings[];
+extern __code const uint8_t * __code const hex;
+extern __code const struct f_data f_data[];
+extern __code const char * __code const mime_strings[];
 extern __xdata struct flash_region_t flash_region;
 extern __xdata uint32_t flash_size;
 
@@ -127,7 +127,7 @@ uint8_t find_entry(__xdata uint8_t *e)
 }
 
 
-bool is_word(__xdata uint8_t *xdata_str_p, __code uint8_t * __xdata code_str_p)
+bool is_word(__xdata uint8_t *xdata_str_p, __code const uint8_t * __xdata code_str_p)
 {
 	uint8_t u, c;
 
@@ -149,7 +149,7 @@ bool is_word(__xdata uint8_t *xdata_str_p, __code uint8_t * __xdata code_str_p)
 
 
 /* name must be lower-case, starting with the '\n' of the previous line's end */
-__xdata uint8_t *header_value(__xdata uint8_t *p, __code uint8_t *name)
+__xdata uint8_t *header_value(__xdata uint8_t *p, __code const uint8_t *name)
 {
 	uint8_t u, c;
 
diff --git a/httpd/page_impl.c b/httpd/page_impl.c
index 58624145..e7cdebe8 100644
--- a/httpd/page_impl.c
+++ b/httpd/page_impl.c
@@ -30,7 +30,7 @@ extern __xdata uint16_t slen;
 extern __xdata uint16_t management_vlan;
 extern __xdata uint16_t cont_len;
 extern __xdata uint32_t cont_addr;
-extern __code uint8_t * __code hex;
+extern __code const uint8_t * __code const hex;
 extern __xdata uip_ipaddr_t uip_hostaddr, uip_draddr, uip_netmask;
 
 extern __xdata uint8_t sfr_data[4];
@@ -47,8 +47,8 @@ extern __xdata char sfp_module_model[2][17];
 extern __xdata char sfp_module_serial[2][17];
 extern __xdata uint8_t sfp_options[2];
 
-__code uint8_t * __code HTTP_RESPONCE_JSON = "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Type: application/json\r\n\r\n";
-__code uint8_t * __code HTTP_RESPONCE_TXT = "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Type: text/plain\r\n\r\n";
+__code const uint8_t * __code const HTTP_RESPONCE_JSON = "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Type: application/json\r\n\r\n";
+__code const uint8_t * __code const HTTP_RESPONCE_TXT = "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Type: text/plain\r\n\r\n";
 
 // Convert uint8_t to ascii HEX char push on html-buffer.
 void charhex_to_html(char c)
@@ -127,7 +127,7 @@ void itoa16_html(uint16_t v) /* sufficient for VLAN IDs (max 4094) */
 	char_to_html('0' + (v % 10));
 }
 
-void string_to_html(__code char *s)
+void string_to_html(__code const char *s)
 {
 	while (*s) char_to_html(*s++);
 }
diff --git a/httpd/page_impl.h b/httpd/page_impl.h
index cad4cd6f..0f171042 100644
--- a/httpd/page_impl.h
+++ b/httpd/page_impl.h
@@ -3,7 +3,7 @@
 
 #include <stdbool.h>
 
-extern __code uint8_t * __code HTTP_RESPONCE_TXT;
+extern __code const uint8_t * __code const HTTP_RESPONCE_TXT;
 
 bool send_counters(uint8_t phys_port);
 void send_status(void);
diff --git a/installer/installer.c b/installer/installer.c
index f86b7821..18dbdfdd 100644
--- a/installer/installer.c
+++ b/installer/installer.c
@@ -30,7 +30,7 @@
 __xdata uint8_t buffer[0x1000];
 __xdata uint8_t dio_enabled;
 
-__code uint8_t * __code hex = "0123456789abcdef";
+__code const uint8_t * __code const hex = "0123456789abcdef";
 
 void isr_timer0(void) __interrupt(1)
 {
@@ -67,7 +67,7 @@ void write_char(char c)
 }
 
 
-void print_string(__code char *p)
+void print_string(__code const char *p)
 {
 	while (*p)
 		write_char(*p++);
diff --git a/rtl837x_common.h b/rtl837x_common.h
index 2ae75fdf..5e1373f8 100644
--- a/rtl837x_common.h
+++ b/rtl837x_common.h
@@ -183,13 +183,13 @@ uint16_t strlen(__code const char *s);
 uint16_t strcpy(__xdata uint8_t *dst, const char *s);
 char strcmp(__xdata const uint8_t *a, __code const uint8_t *b);
 #endif
-void memcpyc(__xdata uint8_t *dst, __code uint8_t *src, uint16_t len);
+void memcpyc(__xdata uint8_t *dst, __code const uint8_t *src, uint16_t len);
 uint16_t strlen_x(__xdata const char *s);
 uint16_t strtox(__xdata uint8_t *dst, __code const char *s);
 bool strstart(__xdata const uint8_t *a, __code const uint8_t *b);
 bool strstart_x(__xdata const uint8_t *a, __xdata const uint8_t *b);
 void tcpip_output(void);
-uint8_t read_flash(uint8_t bank, __code uint8_t *addr);
+uint8_t read_flash(uint8_t bank, __code const uint8_t *addr);
 void get_random_32(void);
 void read_reg_timer(__xdata uint32_t * tmr);
 bool gpio_pin_test(uint8_t pin);
diff --git a/rtl837x_flash.c b/rtl837x_flash.c
index 2ec5bc3f..c1357b04 100644
--- a/rtl837x_flash.c
+++ b/rtl837x_flash.c
@@ -171,7 +171,7 @@ void flash_read_uid(void)
 	flash_configure_mmio();
 }
 
-__code char* get_flash_size_str(void)
+__code const char* get_flash_size_str(void)
 {
 	switch (flash_capacity_code) {
 		case 0x12: return "256 KB";
diff --git a/rtl837x_flash.h b/rtl837x_flash.h
index eef25b14..f7fc4790 100644
--- a/rtl837x_flash.h
+++ b/rtl837x_flash.h
@@ -19,7 +19,7 @@ void flash_read_security(void);
 void flash_sector_erase(void);
 void flash_read_bulk(__xdata uint8_t *dst);
 void flash_write_bytes(__xdata uint8_t *ptr);
-__code char* get_flash_size_str(void);
+__code const char* get_flash_size_str(void);
 
 #endif
 
diff --git a/rtl837x_igmp.c b/rtl837x_igmp.c
index 0a749f99..ce786e75 100644
--- a/rtl837x_igmp.c
+++ b/rtl837x_igmp.c
@@ -15,7 +15,7 @@
 #include "rtl837x_igmp.h"
 #include "machine.h"
 
-extern __code struct machine machine;
+extern __code const struct machine machine;
 extern __xdata uint8_t igmpEnabled;
 
 #include "uip.h"
diff --git a/rtl837x_init.c b/rtl837x_init.c
index 6b24843b..b227e189 100644
--- a/rtl837x_init.c
+++ b/rtl837x_init.c
@@ -9,7 +9,7 @@
 #include "boot.h"
 
 extern __xdata uint8_t sfr_data[4];
-extern __code struct machine machine;
+extern __code const struct machine machine;
 extern __xdata struct machine_runtime machine_detected;
 
 #pragma codeseg BANK2
diff --git a/rtl837x_leds.c b/rtl837x_leds.c
index d0aa498b..4811cafa 100644
--- a/rtl837x_leds.c
+++ b/rtl837x_leds.c
@@ -15,7 +15,7 @@
 #include "rtl837x_leds.h"
 #include "machine.h"
 
-extern __code struct machine machine;
+extern __code const struct machine machine;
 
 #include "uip.h"
 
@@ -261,7 +261,7 @@ void leds_setup(void) __banked
 	sfr_data[3] = sfr_data[2] = sfr_data[1] = sfr_data[0] = 0;
 	reg_write_m(RTL837X_REG_LED3_0_SET1);
 	reg_write_m(RTL837X_REG_LED3_0_SET3);
-	__code uint8_t * __xdata lptr = &machine.led_sets[0][0];
+	__code const uint8_t * __xdata lptr = &machine.led_sets[0][0];
 	for (__xdata uint8_t set = 0; set < 4; set++) {
 		sfr_data[0] = *(lptr + 5);
 		sfr_data[1] = *(lptr + 4);
diff --git a/rtl837x_phy.c b/rtl837x_phy.c
index 25f7e150..525e3fa2 100644
--- a/rtl837x_phy.c
+++ b/rtl837x_phy.c
@@ -20,7 +20,7 @@
 #pragma codeseg BANK2
 #pragma constseg BANK2
 
-extern __code uint16_t bit_mask[16];
+extern __code const uint16_t bit_mask[16];
 extern __code const struct machine machine;
 extern __xdata struct machine_runtime machine_detected;
 
@@ -33,7 +33,7 @@ __xdata struct phy_settings phy_settings;
 // Note: Adding `Swapping the RX for N-devices`-setting on the end of the array, didn't work.
 // Setting will apply but still no packets flow.
 // Settings are `0x2000, 0xc10c`,
-__code uint16_t rtl8224_sds0_setttings[42] = {
+__code const uint16_t rtl8224_sds0_setttings[42] = {
 	// SDS_DATA, SDS_CMD
 	0x4480, 0xc842,
 	0x0400, 0xc9c2,
diff --git a/rtl837x_port.c b/rtl837x_port.c
index 0383aae3..8cb626c3 100644
--- a/rtl837x_port.c
+++ b/rtl837x_port.c
@@ -18,9 +18,9 @@
 #pragma codeseg BANK1
 #pragma constseg BANK1
 
-extern __code uint8_t * __code hex;
-extern __code uint16_t bit_mask[16];
-extern __code struct machine machine;
+extern __code const uint8_t * __code const hex;
+extern __code const uint16_t bit_mask[16];
+extern __code const struct machine machine;
 extern __xdata uint8_t sfr_data[4];
 extern __xdata uint16_t vlan_ptr;
 extern __xdata uint8_t vlan_names[VLAN_NAMES_SIZE];
diff --git a/rtl837x_stp.c b/rtl837x_stp.c
index f7eb871b..26e14806 100644
--- a/rtl837x_stp.c
+++ b/rtl837x_stp.c
@@ -22,7 +22,7 @@ extern __xdata uint8_t err_status;
 #pragma codeseg BANK2
 #pragma constseg BANK2
 
-extern __code struct machine machine;
+extern __code const struct machine machine;
 extern __xdata uint8_t sfr_data[4];
 extern __xdata struct machine_runtime machine_detected;
 
@@ -35,7 +35,7 @@ extern __xdata uint8_t cmd_buffer[CMD_BUF_SIZE];
 extern __xdata uint8_t cmd_words_len;
 extern __xdata uint8_t cmd_words_b[15];
 extern __xdata char save_cmd;		/* 0 while execute_config() replays the saved config */
-uint8_t cmd_compare(uint8_t start, __code uint8_t * cmd);
+uint8_t cmd_compare(uint8_t start, __code const uint8_t * cmd);
 uint8_t atoi_byte(uint8_t idx);
 uint8_t cmd_parse_port_separator(uint8_t idx);
 extern __xdata uint8_t atoi_results_u8;
diff --git a/rtlplayground.c b/rtlplayground.c
index 1a2ed442..6b0bf2df 100644
--- a/rtlplayground.c
+++ b/rtlplayground.c
@@ -79,9 +79,9 @@ void crc16_bank1(__xdata uint8_t *v) __naked;
 
 __xdata uint8_t idle_ready;
 
-__code uint8_t ownIP[] = { 192, 168, 2, 2 };
-__code uint8_t gatewayIP[] = { 192, 168, 2, 22};
-__code uint8_t netmask[] = { 255, 255, 255, 0};
+__code const uint8_t ownIP[] = { 192, 168, 2, 2 };
+__code const uint8_t gatewayIP[] = { 192, 168, 2, 22};
+__code const uint8_t netmask[] = { 255, 255, 255, 0};
 
 __xdata struct uip_eth_addr uip_ethaddr;
 
@@ -108,8 +108,8 @@ extern __xdata uint8_t gpio_last_value[8];
 
 extern __xdata struct flash_region_t flash_region;
 
-__code uint8_t * __code greeting = "\nA minimal prompt to explore the RTL8372:\n";
-__code uint8_t * __code hex = "0123456789abcdef";
+__code const uint8_t * __code const greeting = "\nA minimal prompt to explore the RTL8372:\n";
+__code const uint8_t * __code const hex = "0123456789abcdef";
 
 __xdata uint8_t flash_buf[FLASH_BUF_SIZE];
 
@@ -126,7 +126,7 @@ __xdata bool stp_enabled;
 __xdata uint8_t igmpEnabled;
 __xdata char hostname[24];	/* device hostname, default set at boot, see rtl837x_common.h */
 
-__code uint16_t bit_mask[16] = {
+__code const uint16_t bit_mask[16] = {
 	0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
 	0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000, 0x8000
 };
@@ -349,7 +349,7 @@ int memcmp(__xdata const void *a, __xdata const void *b, uint16_t len)
 	return 0;
 }
 
-void memcpyc(__xdata uint8_t *dst, __code uint8_t *src, uint16_t len)
+void memcpyc(__xdata uint8_t *dst, __code const uint8_t *src, uint16_t len)
 {
 	while (len--)
 		*dst++ = *src++;
@@ -785,7 +785,7 @@ void nic_tx_packet(uint16_t ring_ptr)
  * Note that the address in the flash memory is not simply 0xbbaddr, because
  * the size of a bank is merely 0xc000.
  */
-uint8_t read_flash(uint8_t bank, __code uint8_t *addr)
+uint8_t read_flash(uint8_t bank, __code const uint8_t *addr)
 {
 	uint8_t v;
 	uint8_t current_bank = PSBANK;
diff --git a/sfp.c b/sfp.c
index 1f1f6652..9866929a 100644
--- a/sfp.c
+++ b/sfp.c
@@ -35,12 +35,12 @@ __code enum sfp_quirk {
 };
 
 struct sfp_quirk_entry {
-	__code char *vendor; // Set vendor or model to 0 to act as wildcard
-	__code char *model;
+	__code const char *vendor; // Set vendor or model to 0 to act as wildcard
+	__code const char *model;
 	uint8_t quirks;
 };
 
-static __code struct sfp_quirk_entry sfp_quirk_table[] = {
+static __code const struct sfp_quirk_entry sfp_quirk_table[] = {
 	{ "QSFPTEK", "QT-SFP+-T", SFP_QUIRK_DDM },
 };
 
diff --git a/test/env_tables.c b/test/env_tables.c
index 4d31fb65..274a67d5 100644
--- a/test/env_tables.c
+++ b/test/env_tables.c
@@ -90,7 +90,7 @@ struct uip_eth_addr uip_ethaddr = { .addr = { 0x02, 0x11, 0x22, 0x33, 0x44, 0x55
 
 /* ---- leaf calls into subsystems not under test ---- */
 void     flash_read_bulk(uint8_t *dst) { (void)dst; }
-char    *get_flash_size_str(void) { return (char *)"2M"; }
+const char *get_flash_size_str(void) { return "2M"; }
 uint8_t  sfp_read_reg(uint8_t slot, uint8_t reg) { (void)slot; (void)reg; return 0; }
 bool     gpio_pin_test(uint8_t pin) { (void)pin; return false; }
 void     phy_read(uint8_t phy_id, uint8_t dev_id, uint16_t reg) { (void)phy_id; (void)dev_id; (void)reg; }
diff --git a/test/stub/html_data.h b/test/stub/html_data.h
index 6e7f0029..c15f9f26 100644
--- a/test/stub/html_data.h
+++ b/test/stub/html_data.h
@@ -5,7 +5,7 @@
 #define FDATA_DEFS_H
 #include <stdint.h>
 typedef enum mime_type_e { mime_HTML = 0, mime_SVG, mime_ICO, mime_PNG, mime_JS, mime_CSS, mime_TXT } mime_type_t;
-struct f_data { __code char *file; uint32_t start; uint16_t len; mime_type_t mime; uint8_t gzip; };
+struct f_data { __code const char *file; uint32_t start; uint16_t len; mime_type_t mime; uint8_t gzip; };
 #define FDATA_START_login_html		0x00040000UL
 #define FDATA_START_favicon_ico		0x00041000UL
 #endif
diff --git a/test/test_httpd_tx.c b/test/test_httpd_tx.c
index 3a82b343..6f464d2b 100644
--- a/test/test_httpd_tx.c
+++ b/test/test_httpd_tx.c
@@ -67,18 +67,18 @@ volatile uint8_t sfr_data[4];
 volatile uint32_t ticks;
 uint8_t cmd_capture;
 uint8_t err_status;
-uint8_t *hex = (uint8_t *)"0123456789abcdef";
+const uint8_t * const hex = (const uint8_t *)"0123456789abcdef";
 uint16_t crc_value;
-uint8_t *HTTP_RESPONCE_TXT = (uint8_t *)"HTTP/1.1 200 OK\r\n\r\n";
+const uint8_t * const HTTP_RESPONCE_TXT = (const uint8_t *)"HTTP/1.1 200 OK\r\n\r\n";
 uint32_t flash_size = 0x80000;
 uint8_t flash_buf[FLASH_BUF_SIZE];
 uint8_t rx_headers[16];
 struct flash_region_t flash_region;
 
-char *mime_strings[] = { "text/html", "image/svg+xml", "image/x-icon",
+const char * const mime_strings[] = { "text/html", "image/svg+xml", "image/x-icon",
 			 "image/png", "text/javascript", "text/css", "text/plain" };
 
-struct f_data f_data[] = {
+const struct f_data f_data[] = {
 	{ FILE_NAME, FILE_START, FILE_LEN, mime_HTML, 0 },
 	{ 0, 0, 0, mime_HTML, 0 },
 };
@@ -92,7 +92,7 @@ void flash_read_bulk(uint8_t *dst)
 void flash_init(uint8_t enable_dio) { (void)enable_dio; }
 void flash_sector_erase(void) { }
 void flash_write_bytes(uint8_t *ptr) { (void)ptr; }
-char *get_flash_size_str(void) { return "512 kB"; }
+const char *get_flash_size_str(void) { return "512 kB"; }
 void crc16_bank1(uint8_t *v) { (void)v; }
 void reset_chip(void) { }
 void delay(uint16_t t) { (void)t; }
@@ -124,7 +124,7 @@ uint16_t strtox(uint8_t *dst, const char *s)
 	return n;
 }
 
-void memcpyc(uint8_t *dst, uint8_t *src, uint16_t len) { memcpy(dst, src, len); }
+void memcpyc(uint8_t *dst, const uint8_t *src, uint16_t len) { memcpy(dst, src, len); }
 
 bool strstart(const uint8_t *a, const uint8_t *b)
 {
diff --git a/tools/fileadder.c b/tools/fileadder.c
index c9022b91..1da276ec 100644
--- a/tools/fileadder.c
+++ b/tools/fileadder.c
@@ -318,7 +318,7 @@ int main(int argc, char **argv)
 	defbuf_p += snprintf(&dbuf[defbuf_p], DEF_SIZE - defbuf_p, "#include <stdint.h>\n\n");
 	defbuf_p += snprintf(&dbuf[defbuf_p], DEF_SIZE - defbuf_p,
 			     "typedef enum mime_type_e {\n  mime_HTML = 0,\n  mime_SVG,\n  mime_ICO,\n  mime_PNG,\n  mime_JS,\n  mime_CSS,\n  mime_TXT\n} mime_type_t;\n\n");
-	defbuf_p += snprintf(&dbuf[defbuf_p], DEF_SIZE - defbuf_p, "struct f_data {\n  __code char *file;\n  uint32_t start;\n  uint16_t len;\n  mime_type_t mime;\n  uint8_t gzip;\n};\n\n");
+	defbuf_p += snprintf(&dbuf[defbuf_p], DEF_SIZE - defbuf_p, "struct f_data {\n  __code const char *file;\n  uint32_t start;\n  uint16_t len;\n  mime_type_t mime;\n  uint8_t gzip;\n};\n\n");
 	// defbuf_p += snprintf(&dbuf[defbuf_p], DEF_SIZE - defbuf_p, "typedef uint16_t (* fcall_ptr)(void);\n\n");
 
 	ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, "// This file is automatically generated, do not edit!\n\n");
@@ -326,9 +326,9 @@ int main(int argc, char **argv)
 		ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, "#include \"%s.h\"\n\n", arguments.prefix);
 	if (arguments.bank)
 		ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, "#pragma codeseg %s\n#pragma constseg %s\n\n", arguments.bank, arguments.bank);
-	ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, " __code char * __code mime_strings[] = {\n  \"text/html\",\n  \"image/svg+xml\",\n"
+	ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, " __code const char * __code const mime_strings[] = {\n  \"text/html\",\n  \"image/svg+xml\",\n"
 		"  \"image/svg+xml\",\n  \"image/png\",\n  \"text/javascript\",\n  \"text/css\",\n  \"text/plain\"};\n\n");
-	ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, "__code struct f_data f_data[] = {\n");
+	ibuf_p += snprintf(&ibuf[ibuf_p], INDEX_SIZE - ibuf_p, "__code const struct f_data f_data[] = {\n");
 	// fbuf_p += snprintf(&fbuf[fbuf_p], DEF_SIZE - fbuf_p, "\n__code fcall_ptr f_calls[] = {\n");
 
 	// Now that the beginning of the buffer is filled with out image, optionally resize the image
diff --git a/uip/uip.h b/uip/uip.h
index 5f4d8e29..1fab85ea 100644
--- a/uip/uip.h
+++ b/uip/uip.h
@@ -912,8 +912,8 @@ __xdata struct uip_udp_conn *uip_udp_new(__xdata uip_ipaddr_t * __xdata ripaddr,
 				      ((__xdata u16_t *)addr1)[1] == ((__xdata u16_t *)addr2)[1])
 #define uip_ipaddr_cmpx(addr1, addr2) (((__xdata u16_t *)addr1)[0] == ((__xdata u16_t *)addr2)[0] && \
 				      ((__xdata u16_t *)addr1)[1] == ((__xdata u16_t *)addr2)[1])
-#define uip_ipaddr_cmpc(addr1, addr2) (((__xdata u16_t *)addr1)[0] == ((__code u16_t *)addr2)[0] && \
-				      ((__xdata u16_t *)addr1)[1] == ((__code u16_t *)addr2)[1])
+#define uip_ipaddr_cmpc(addr1, addr2) (((__xdata u16_t *)addr1)[0] == ((__code const u16_t *)addr2)[0] && \
+				      ((__xdata u16_t *)addr1)[1] == ((__code const u16_t *)addr2)[1])
 #else /* !UIP_CONF_IPV6 */
 #define uip_ipaddr_cmp(addr1, addr2) (memcmp(addr1, addr2, sizeof(uip_ip6addr_t)) == 0)
 #endif /* !UIP_CONF_IPV6 */