diff --git a/soem/ethercatcoe.c b/soem/ethercatcoe.c
index a5ce212..86667b5 100644
--- a/soem/ethercatcoe.c
+++ b/soem/ethercatcoe.c
@@ -856,13 +856,11 @@ int ecx_readPDOmap(ecx_contextt *context, uint16 Slave, int *Osize, int *Isize)
    /* positive result from slave ? */
    if ((wkc > 0) && (nSM > 2))
    {
-      /* make nSM equal to number of defined SM */
-      nSM--;
       /* limit to maximum number of SM defined, if true the slave can't be configured */
       if (nSM > EC_MAXSM)
          nSM = EC_MAXSM;
       /* iterate for every SM type defined */
-      for (iSM = 2 ; iSM <= nSM ; iSM++)
+      for (iSM = 2 ; iSM < nSM ; iSM++)
       {
          rdl = sizeof(tSM); tSM = 0;
          /* read SyncManager Communication Type */
@@ -958,8 +956,7 @@ int ecx_readPDOmapCA(ecx_contextt *context, uint16 Slave, int *Osize, int *Isize
    /* positive result from slave ? */
    if ((wkc > 0) && (context->SMcommtype->n > 2))
    {
-      /* make nSM equal to number of defined SM */
-      nSM = context->SMcommtype->n - 1;
+      nSM = context->SMcommtype->n;
       /* limit to maximum number of SM defined, if true the slave can't be configured */
       if (nSM > EC_MAXSM)
       {
@@ -967,7 +964,7 @@ int ecx_readPDOmapCA(ecx_contextt *context, uint16 Slave, int *Osize, int *Isize
          ecx_packeterror(context, Slave, 0, 0, 10); /* #SM larger than EC_MAXSM */
       }
       /* iterate for every SM type defined */
-      for (iSM = 2 ; iSM <= nSM ; iSM++)
+      for (iSM = 2 ; iSM < nSM ; iSM++)
       {
          tSM = context->SMcommtype->SMtype[iSM];