diff --git a/host/host.c b/host/host.c
index 27860bc..9519cc6 100644
--- a/host/host.c
+++ b/host/host.c
@@ -171,6 +171,7 @@ int main(int argc, char *argv[]) {
                 printf("UVM32_EVT_ERR '%s' (%d)\n", evt.data.err.errstr, (int)evt.data.err.errcode);
                 if (evt.data.err.errcode == UVM32_ERR_HUNG) {
                     printf("VM may have hung, increase max_instrs_per_run\n");
+                    uvm32_clearError(&vmst);    // allow to continue
                 } else {
                     isrunning = false;
                 }
diff --git a/test/Makefile b/test/Makefile
index 1bf09ef..a2befe3 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,4 +1,10 @@
-TESTS = example_1 stackoverflow custom_syscall
+TESTS = \
+    basic_syscalls  \
+    stackoverflow   \
+    custom_syscall  \
+    syscall_args \
+    meter
+
 RUNCMD = $(foreach TEST,${TESTS},make -C ${TEST} &&)
 CLEANCMD = $(foreach TEST,${TESTS},make -C ${TEST} clean &&)
 
diff --git a/test/example_1/Makefile b/test/basic_syscalls/Makefile
similarity index 100%
rename from test/example_1/Makefile
rename to test/basic_syscalls/Makefile
diff --git a/test/example_1/rom/Makefile b/test/basic_syscalls/rom/Makefile
similarity index 100%
rename from test/example_1/rom/Makefile
rename to test/basic_syscalls/rom/Makefile
diff --git a/test/basic_syscalls/rom/rom.c b/test/basic_syscalls/rom/rom.c
new file mode 100644
index 0000000..ea40b79
--- /dev/null
+++ b/test/basic_syscalls/rom/rom.c
@@ -0,0 +1,10 @@
+#include "uvm32_target.h"
+
+void main(void) {
+    println("Hello world");
+    print("Hello world");
+    printdec(42);
+    printhex(0xDEADBEEF);
+    putc('G');
+}
+
diff --git a/test/basic_syscalls/test/tests.c b/test/basic_syscalls/test/tests.c
new file mode 100644
index 0000000..c5d2f5a
--- /dev/null
+++ b/test/basic_syscalls/test/tests.c
@@ -0,0 +1,56 @@
+#include <string.h>
+#include "unity.h"
+#include "uvm32.h"
+#include "../common/uvm32_common_custom.h"
+
+#include "rom-header.h"
+
+static uvm32_state_t vmst;
+static uvm32_evt_t evt;
+
+void setUp(void) {
+    // runs before each test
+    uvm32_init(&vmst);
+    uvm32_load(&vmst, rom_bin, rom_bin_len);
+}
+
+void tearDown(void) {
+}
+
+void test_syscalls(void) {
+    // check for println syscall
+    uvm32_run(&vmst, &evt, 1000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
+    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PRINTLN);
+    TEST_ASSERT_EQUAL(0, strcmp(uvm32_getcstr(&vmst, &evt, ARG0), "Hello world"));
+
+    // check for print syscall
+    uvm32_run(&vmst, &evt, 1000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
+    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PRINT);
+    TEST_ASSERT_EQUAL(0, strcmp(uvm32_getcstr(&vmst, &evt, ARG0), "Hello world"));
+
+    // check for printdec syscall
+    uvm32_run(&vmst, &evt, 1000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
+    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PRINTDEC);
+    TEST_ASSERT_EQUAL(42, uvm32_getval(&vmst, &evt, ARG0));
+
+    // check for printhex syscall
+    uvm32_run(&vmst, &evt, 1000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
+    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PRINTHEX);
+    TEST_ASSERT_EQUAL(0xDEADBEEF, uvm32_getval(&vmst, &evt, ARG0));
+
+    // check for putc syscall
+    uvm32_run(&vmst, &evt, 1000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
+    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PUTC);
+    TEST_ASSERT_EQUAL('G', uvm32_getval(&vmst, &evt, ARG0));
+
+    // run vm to completion
+    uvm32_run(&vmst, &evt, 10000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_END);
+}
+
+
diff --git a/test/example_1/rom/rom.c b/test/example_1/rom/rom.c
deleted file mode 100644
index 072ab1d..0000000
--- a/test/example_1/rom/rom.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include "uvm32_target.h"
-
-void main(void) {
-    println("Hello world");
-}
-
diff --git a/test/example_1/test/tests.c b/test/example_1/test/tests.c
deleted file mode 100644
index 37585ce..0000000
--- a/test/example_1/test/tests.c
+++ /dev/null
@@ -1,33 +0,0 @@
-#include <string.h>
-#include "unity.h"
-#include "uvm32.h"
-#include "../common/uvm32_common_custom.h"
-
-#include "rom-header.h"
-
-static uvm32_state_t vmst;
-static uvm32_evt_t evt;
-
-void setUp(void) {
-    // runs before each test
-    uvm32_init(&vmst);
-    uvm32_load(&vmst, rom_bin, rom_bin_len);
-}
-
-void tearDown(void) {
-}
-
-void test_helloworld1(void) {
-    // run the vm
-    uvm32_run(&vmst, &evt, 10000);
-    // check for println syscall
-    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_SYSCALL);
-    TEST_ASSERT_EQUAL(evt.data.syscall.code, UVM32_SYSCALL_PRINTLN);
-    const char *str = uvm32_getcstr(&vmst, &evt, ARG0);
-    TEST_ASSERT_EQUAL(0, strcmp(str, "Hello world"));
-    // run vm to completion
-    uvm32_run(&vmst, &evt, 10000);
-    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_END);
-}
-
-
diff --git a/test/meter/Makefile b/test/meter/Makefile
new file mode 100644
index 0000000..6533b02
--- /dev/null
+++ b/test/meter/Makefile
@@ -0,0 +1,33 @@
+C_COMPILER=gcc
+
+UNITY_ROOT=../unity
+
+CFLAGS=-std=c99
+CFLAGS += -Wall
+CFLAGS += -Werror
+CFLAGS += -DUVM32_MEMORY_SIZE=16384
+
+SUITE_NAME=tests
+
+TARGET_BASE1=test1
+TARGET1 = $(TARGET_BASE1)
+SRC_FILES1=$(UNITY_ROOT)/src/unity.c test/${SUITE_NAME}.c  test/test_runners/${SUITE_NAME}_Runner.c ../../uvm32/uvm32.c
+INC_DIRS=-I$(UNITY_ROOT)/src -I../../uvm32/ -I../../common -Irom
+
+.PHONY: rom
+
+default: $(SRC_FILES1) rom
+	@$(C_COMPILER) $(CFLAGS) $(INC_DIRS) $(SYMBOLS) $(SRC_FILES1) rom/rom-header.c -o $(TARGET1)
+	@ ./$(TARGET1)
+
+rom:
+	@(cd rom && make)
+
+test/test_runners/${SUITE_NAME}_Runner.c: test/${SUITE_NAME}.c
+	@mkdir -p test/test_runners
+	@ruby $(UNITY_ROOT)/auto/generate_test_runner.rb test/${SUITE_NAME}.c  test/test_runners/${SUITE_NAME}_Runner.c
+
+clean:
+	rm -rf $(TARGET1) test/test_runners
+	(cd rom && make clean)
+
diff --git a/test/meter/rom/Makefile b/test/meter/rom/Makefile
new file mode 100644
index 0000000..9f50d69
--- /dev/null
+++ b/test/meter/rom/Makefile
@@ -0,0 +1,14 @@
+TOPDIR=../../../
+PROJECT:=$(shell basename ${PWD})
+SRCS=${PROJECT}.c ${TOPDIR}/apps/crt0.S
+OPT=-O0 # don't let optimiser remove stall loop
+all: all_common
+	@# Convert ROM to C file and header
+	@xxd -i ${PROJECT}.bin > ${PROJECT}-header.c
+	@echo "extern unsigned char ${PROJECT}_bin[]; extern int ${PROJECT}_bin_len;" > ${PROJECT}-header.h
+
+test: test_common
+clean: clean_common
+	rm -f ${PROJECT}-header.h ${PROJECT}-header.c
+
+include ${TOPDIR}/apps/makefile.common
diff --git a/test/meter/rom/rom.c b/test/meter/rom/rom.c
new file mode 100644
index 0000000..823862e
--- /dev/null
+++ b/test/meter/rom/rom.c
@@ -0,0 +1,15 @@
+#include "uvm32_target.h"
+
+void stall(void) {
+    volatile uint32_t i;
+    for (i=0;i<100;i++) {
+    }
+}
+
+void main(void) {
+    for (int i=0;i<100;i++) {
+        stall();
+        printdec(i);
+    }
+}
+
diff --git a/test/meter/test/tests.c b/test/meter/test/tests.c
new file mode 100644
index 0000000..8999e1c
--- /dev/null
+++ b/test/meter/test/tests.c
@@ -0,0 +1,58 @@
+#include <string.h>
+#include "unity.h"
+#include "uvm32.h"
+#include "../common/uvm32_common_custom.h"
+
+#include "rom-header.h"
+
+static uvm32_state_t vmst;
+static uvm32_evt_t evt;
+
+void setUp(void) {
+    // runs before each test
+    uvm32_init(&vmst);
+    uvm32_load(&vmst, rom_bin, rom_bin_len);
+}
+
+void tearDown(void) {
+}
+
+// run program until printdec() reaches 100
+// every time it hangs, resume
+// run in batches of num_instr
+void metered_run(uint32_t num_instr) {
+    uint32_t expected = 0;
+
+    while(expected < 100) {
+        uvm32_run(&vmst, &evt, num_instr);
+        switch(evt.typ) {
+            case UVM32_EVT_SYSCALL: {
+                TEST_ASSERT_EQUAL(UVM32_SYSCALL_PRINTDEC, evt.data.syscall.code);
+                uint32_t val = uvm32_getval(&vmst, &evt, ARG0);
+                TEST_ASSERT_EQUAL(val, expected);
+                expected++;
+            } break;
+            case UVM32_EVT_ERR:
+                TEST_ASSERT_EQUAL(evt.data.err.errcode, UVM32_ERR_HUNG);
+                uvm32_clearError(&vmst);    // clear the hung error so it can continue
+            break;
+            case UVM32_EVT_END:
+                TEST_ASSERT_EQUAL(0, 1);    // trigger an assert, we didn't get to 100000 yet
+            break;
+        }
+    }
+
+    // run vm to completion
+    uvm32_run(&vmst, &evt, 10000);
+    TEST_ASSERT_EQUAL(evt.typ, UVM32_EVT_END);
+}
+
+void test_meter(void) {
+    // test many different meter values, including 0 (which should run 1 instruction, as 0 is going to hang)
+    for (uint32_t i=0;i<1000;i++) {
+        uvm32_init(&vmst);
+        uvm32_load(&vmst, rom_bin, rom_bin_len);
+        metered_run(i);
+    }
+}
+
diff --git a/uvm32/uvm32.c b/uvm32/uvm32.c
index 550d302..f5ba520 100644
--- a/uvm32/uvm32.c
+++ b/uvm32/uvm32.c
@@ -138,27 +138,33 @@ void uvm32_clearError(uvm32_state_t *vmst) {
 }
 
 uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter) {
-    uint32_t num_instr = 0;
+    const uint32_t min_instrs = 1;
+    uint32_t orig_instr_meter = instr_meter;
+
+    if (instr_meter < min_instrs) {
+        instr_meter = min_instrs;
+    }
 
     if (vmst->stack_canary != UVM32_NULL && *vmst->stack_canary != STACK_CANARY_VALUE) {
         setStatusErr(vmst, UVM32_ERR_INTERNAL_CORE);
         setup_err_evt(vmst, evt);
-        return num_instr;
+        return orig_instr_meter - instr_meter;
     }
 
     if (vmst->status != UVM32_STATUS_PAUSED) {
         setStatusErr(vmst, UVM32_ERR_NOTREADY);
         setup_err_evt(vmst, evt);
-        return num_instr;
+        return orig_instr_meter - instr_meter;
     }
 
     setStatus(vmst, UVM32_STATUS_RUNNING);
 
     // run CPU until no longer in running state
-    while(vmst->status == UVM32_STATUS_RUNNING) {
+    while(vmst->status == UVM32_STATUS_RUNNING && instr_meter > 0) {
         uint64_t elapsedUs = 1;
         uint32_t ret;
         ret = MiniRV32IMAStep(vmst, &vmst->core, vmst->memory, 0, elapsedUs, 1);
+        instr_meter--;
     
         switch(ret) {
             case 0:  // ok
@@ -213,28 +219,25 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
             break;
         }
 
-        num_instr++;
-
-        // check instruction meter, in case of hang/infinite loop
-        if (instr_meter-- == 0) {
+        if (vmst->status == UVM32_STATUS_RUNNING && instr_meter == 0) {
+            // no syscall occurred, so we've hung
             setStatusErr(vmst, UVM32_ERR_HUNG);
             setup_err_evt(vmst, evt);
-            return num_instr;
+            return orig_instr_meter - instr_meter;
         }
-
     }
 
 
     if (vmst->status == UVM32_STATUS_ENDED) {
         evt->typ = UVM32_EVT_END;
-        return num_instr;
+        return orig_instr_meter - instr_meter;
     }
 
     // an event is ready
     if (vmst->status == UVM32_STATUS_PAUSED) {
         // send back the built up event
         UVM32_MEMCPY(evt, &vmst->ioevt, sizeof(uvm32_evt_t));
-        return num_instr;
+        return orig_instr_meter - instr_meter;
     } else {
         if (vmst->status == UVM32_STATUS_ERROR) {
             setup_err_evt(vmst, evt);
@@ -242,7 +245,7 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
             setStatusErr(vmst, UVM32_ERR_INTERNAL_STATE);
             setup_err_evt(vmst, evt);
         }
-        return num_instr;
+        return orig_instr_meter - instr_meter;
     }
 }
 
@@ -301,3 +304,14 @@ uvm32_evt_syscall_buf_t uvm32_getbuf(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm3
     return scb;
 }
 
+uvm32_evt_syscall_buf_t uvm32_getbuf_fixed(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t argPtr, uint32_t len) {
+    uvm32_evt_syscall_buf_t scb;
+    if (!get_safeptr(vmst, uvm32_getval(vmst, evt, argPtr), len, &scb)) {
+        setStatusErr(vmst, UVM32_ERR_MEM_RD);
+        garbage = 0;
+        scb.ptr = (uint8_t *)&garbage;
+        scb.len = 0;
+    }
+    return scb;
+}
+
diff --git a/uvm32/uvm32.h b/uvm32/uvm32.h
index d72a886..6c6fa8e 100644
--- a/uvm32/uvm32.h
+++ b/uvm32/uvm32.h
@@ -97,6 +97,7 @@ uint32_t uvm32_getval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t);
 const char *uvm32_getcstr(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t);
 void uvm32_setval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t, uint32_t val);
 uvm32_evt_syscall_buf_t uvm32_getbuf(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t argPtr, uvm32_arg_t argLen);
+uvm32_evt_syscall_buf_t uvm32_getbuf_fixed(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t argPtr, uint32_t len);
 void uvm32_clearError(uvm32_state_t *vmst);