diff --git a/cmd_parser.c b/cmd_parser.c
index bf266b2..0f94b58 100644
--- a/cmd_parser.c
+++ b/cmd_parser.c
@@ -26,7 +26,7 @@
 #pragma constseg BANK2
 
 extern __code struct machine machine;
-extern __xdata uint8_t stp_enabled;
+extern __xdata bool stp_enabled;
 extern __code uint8_t log_to_phys_port[9];
 
 extern volatile __xdata uint32_t ticks;
diff --git a/rtl837x_common.h b/rtl837x_common.h
index 923d02a..77a31b1 100644
--- a/rtl837x_common.h
+++ b/rtl837x_common.h
@@ -119,7 +119,7 @@ struct flash_region_t {
 
 extern __xdata char port_names[9][PORT_NAME_SIZE];
 
-extern __xdata uint8_t stp_enabled;
+extern __xdata bool stp_enabled;
 
 /* System hostname (device identity). Set via `hostname <text>` and the System
  * Settings page, reported in /information.json. Other modules (e.g. LLDP, which
diff --git a/rtl837x_port.c b/rtl837x_port.c
index b357e58..8eea5a3 100644
--- a/rtl837x_port.c
+++ b/rtl837x_port.c
@@ -323,8 +323,8 @@ void port_l2_forget_port(uint8_t port) __banked
 	REG_SET(RTL837x_L2_TBL_FLUSH_CTRL, L2_TBL_FLUSH_EXEC | (((uint16_t)1) << port));
 
 	do {
-		reg_read_m(RTL837x_L2_TBL_FLUSH_CTRL);
-	} while (sfr_data[1]);
+		reg_read(RTL837x_L2_TBL_FLUSH_CTRL);
+	} while (SFR_DATA_16);
 }
 
 
@@ -421,16 +421,16 @@ void port_l2_learned(void) __banked
 void port_l2mc_set(uint8_t mac_last, __xdata uint16_t vid, __xdata uint16_t pmask) __banked
 {
 	do {
-		reg_read_m(RTL837X_TBL_CTRL);
-	} while (sfr_data[3] & TBL_EXECUTE);
+		reg_read(RTL837X_TBL_CTRL);
+	} while (SFR_DATA_0 & TBL_EXECUTE);
 
 	REG_WRITE(RTL837x_TBL_DATA_IN_A, 0xc2, 0x00, 0x00, mac_last);
 	REG_WRITE(RTL837x_TBL_DATA_IN_B, 0x20 | (vid >> 8) | ((pmask & 0x3) << 6), vid, 0x01, 0x80);
 	REG_WRITE(RTL837x_TBL_DATA_IN_C, 0, 0, 0, pmask >> 2);
 	REG_WRITE(RTL837X_TBL_CTRL, 0, 0, TBL_L2_UNICAST, TBL_WRITE | TBL_EXECUTE);
 	do {
-		reg_read_m(RTL837X_TBL_CTRL);
-	} while (sfr_data[3] & TBL_EXECUTE);
+		reg_read(RTL837X_TBL_CTRL);
+	} while (SFR_DATA_0 & TBL_EXECUTE);
 }
 
 
diff --git a/rtl837x_stp.c b/rtl837x_stp.c
index cc4e916..83d351c 100644
--- a/rtl837x_stp.c
+++ b/rtl837x_stp.c
@@ -254,7 +254,7 @@ static void stp_record_designated(uint8_t port) __reentrant
 /* Lexicographic compare of n bytes. A MAC is 6 of them; a Bridge Identifier
  * is 8, the two priority octets ahead of the MAC, compared as one unsigned
  * number per 802.1D. */
-signed char cmpBytes(__xdata uint8_t *m1, __xdata uint8_t *m2, uint8_t n) __reentrant
+int8_t cmpBytes(__xdata uint8_t *m1, __xdata uint8_t *m2, uint8_t n) __reentrant
 {
 	for (uint8_t i = 0; i < n; i++) {
 		if (m1[i] == m2[i])
diff --git a/rtlplayground.c b/rtlplayground.c
index 23e93fa..a853e42 100644
--- a/rtlplayground.c
+++ b/rtlplayground.c
@@ -121,7 +121,7 @@ __xdata uint16_t management_vlan;
 __xdata bool frame_tagged;
 __xdata uint8_t tx_seq;
 
-__xdata uint8_t stp_enabled;
+__xdata bool stp_enabled;
 __xdata uint8_t igmpEnabled;
 __xdata char hostname[24];	/* device hostname, default set at boot, see rtl837x_common.h */