diff --git a/src/mame/machine/interpro_srarb.cpp b/src/mame/machine/interpro_srarb.cpp
index a389a272317..d3074ea2847 100644
--- a/src/mame/machine/interpro_srarb.cpp
+++ b/src/mame/machine/interpro_srarb.cpp
@@ -25,6 +25,9 @@ DEVICE_ADDRESS_MAP_START(map, 32, interpro_srarb_device)
 	AM_RANGE(0x14, 0x17) AM_READWRITE(errdomhi_r, errdomhi_w)
 	AM_RANGE(0x18, 0x1b) AM_READWRITE(tmctrl_r, tmctrl_w)
 
+	AM_RANGE(0x1c, 0x1f) AM_READWRITE8(unknown0_r, unknown0_w, 0x0000ff00) // boot code writes 0x10
+	AM_RANGE(0x20, 0x23) AM_READWRITE8(unknown1_r, unknown1_w, 0x0000ff00) // boot code writes 0x07
+
 	AM_RANGE(0x24, 0x27) AM_READWRITE(tmsrnem_r, tmsrnem_w)
 	AM_RANGE(0x28, 0x2b) AM_READWRITE(tmsrhog_r, tmsrhog_w)
 	AM_RANGE(0x2c, 0x2f) AM_READWRITE(tmscale_r, tmscale_w)
diff --git a/src/mame/machine/interpro_srarb.h b/src/mame/machine/interpro_srarb.h
index f1b5c9a34d5..d9adccddf20 100644
--- a/src/mame/machine/interpro_srarb.h
+++ b/src/mame/machine/interpro_srarb.h
@@ -15,6 +15,12 @@ public:
 
 	DECLARE_READ32_MEMBER(sdepid_r) { return sdepid; }
 	DECLARE_WRITE32_MEMBER(sdepid_w) { sdepid = data; }
+
+	enum snapid_mask
+	{
+		SNAPID_GRANT   = 0x0000000f,
+		SNAPID_HOGLOCK = 0x000000f0
+	};
 	DECLARE_READ32_MEMBER(snapid_r) { return snapid; }
 	DECLARE_WRITE32_MEMBER(snapid_w) { snapid = data; }
 	DECLARE_READ32_MEMBER(prilo_r) { return prilo; }
@@ -27,8 +33,20 @@ public:
 	DECLARE_READ32_MEMBER(errdomhi_r) { return errdomhi; }
 	DECLARE_WRITE32_MEMBER(errdomhi_w) { errdomhi = data; }
 
+	enum tmctrl_mask
+	{
+		TMCTRL_UNUSED = 0x00000007,
+		TMCTRL_ENNEM  = 0x00000008,
+		TMCTRL_ENHOG  = 0x00000010
+	};
 	DECLARE_READ32_MEMBER(tmctrl_r) { return tmctrl; }
 	DECLARE_WRITE32_MEMBER(tmctrl_w) { tmctrl = data; }
+
+	DECLARE_READ8_MEMBER(unknown0_r) { return unknown0; }
+	DECLARE_WRITE8_MEMBER(unknown0_w) { unknown0 = data; }
+	DECLARE_READ8_MEMBER(unknown1_r) { return unknown1; }
+	DECLARE_WRITE8_MEMBER(unknown1_w) { unknown1 = data; }
+
 	DECLARE_READ32_MEMBER(tmsrnem_r) { return tmsrnem; }
 	DECLARE_WRITE32_MEMBER(tmsrnem_w) { tmsrnem = data; }
 	DECLARE_READ32_MEMBER(tmsrhog_r) { return tmsrhog; }
@@ -44,6 +62,8 @@ private:
 	u32 sdepid, snapid, prilo, prihi;
 	u32 errdomlo, errdomhi;
 	u32 tmctrl, tmsrnem, tmsrhog, tmscale;
+
+	u8 unknown0, unknown1;
 };
 
 // device type definition