diff --git a/libnfc/chips/pn53x.c b/libnfc/chips/pn53x.c
index 1fc9250..26eb0b7 100644
--- a/libnfc/chips/pn53x.c
+++ b/libnfc/chips/pn53x.c
@@ -882,8 +882,6 @@ pn53x_initiator_select_passive_target (nfc_device_t * pnd,
       // Some work to do before getting the UID...
       byte_t abtReqt[]="\x10";
       size_t szReqtLen = 1;
-      byte_t abtRx[2];
-      size_t szRxLen = 2;
       // Getting product code / fab code & store it in output buffer after the serial nr we'll obtain later
       if (!pn53x_initiator_transceive_bytes (pnd, abtReqt, szReqtLen, abtTargetsData+2, &szTargetsData) || szTargetsData != 2) {
         return false;
@@ -897,8 +895,6 @@ pn53x_initiator_select_passive_target (nfc_device_t * pnd,
         return false;
       byte_t abtRead[]="\xC4"; // Reading UID_MSB (Read address 4)
       size_t szReadLen = 1;
-      byte_t abtRx[2];
-      size_t szRxLen = 2;
       if (!pn53x_initiator_transceive_bytes (pnd, abtRead, szReadLen, abtTargetsData+4, &szTargetsData) || szTargetsData != 2) {
         return false;
       }
@@ -1113,20 +1109,19 @@ pn53x_initiator_transceive_bytes (nfc_device_t * pnd, const byte_t * pbtTx, cons
   return true;
 }
 
-// For _timer() functions, the prescaler will dictate what will
-// be the precision and the largest delay to measure before saturation
+void __pn53x_init_timer(nfc_device_t * pnd)
+{
+// The prescaler will dictate what will be the precision and
+// the largest delay to measure before saturation. Some examples:
 // prescaler =  0 => precision:  ~73ns  timer saturates at    ~5ms
 // prescaler =  1 => precision: ~221ns  timer saturates at   ~15ms
 // prescaler =  2 => precision: ~369ns  timer saturates at   ~25ms
 // prescaler = 10 => precision: ~1.5us  timer saturates at  ~100ms
-static uint16_t __timer_prescaler = 0;
-
-void __pn53x_init_timer(nfc_device_t * pnd)
-{
+  CHIP_DATA (pnd)->timer_prescaler = 0;
   uint16_t reloadval = 0xFFFF;
   // Initialize timer
-  pn53x_write_register (pnd, PN53X_REG_CIU_TMode, 0xFF, SYMBOL_TAUTO | ((__timer_prescaler >> 8) & SYMBOL_TPRESCALERHI));
-  pn53x_write_register (pnd, PN53X_REG_CIU_TPrescaler, 0xFF, (__timer_prescaler & SYMBOL_TPRESCALERLO));
+  pn53x_write_register (pnd, PN53X_REG_CIU_TMode, 0xFF, SYMBOL_TAUTO | ((CHIP_DATA (pnd)->timer_prescaler >> 8) & SYMBOL_TPRESCALERHI));
+  pn53x_write_register (pnd, PN53X_REG_CIU_TPrescaler, 0xFF, (CHIP_DATA (pnd)->timer_prescaler & SYMBOL_TPRESCALERLO));
   pn53x_write_register (pnd, PN53X_REG_CIU_TReloadVal_hi, 0xFF, (reloadval >> 8) & 0xFF);
   pn53x_write_register (pnd, PN53X_REG_CIU_TReloadVal_lo, 0xFF, reloadval & 0xFF);
 }
@@ -1165,7 +1160,7 @@ uint32_t __pn53x_get_timer(nfc_device_t * pnd, const uint8_t last_cmd_byte)
   } else {
     u16cycles = 0xFFFF - counter;
     u32cycles = u16cycles;
-    u32cycles *= (__timer_prescaler * 2 + 1);
+    u32cycles *= (CHIP_DATA (pnd)->timer_prescaler * 2 + 1);
     u32cycles++;
     // Correction depending on PN53x Rx detection handling:
     // timer stops after 5 (or 2 for PN531) bits are received
@@ -1198,7 +1193,7 @@ pn53x_initiator_transceive_bits_timed (nfc_device_t * pnd, const byte_t * pbtTx,
   // TODO Do something with these bytes...
   (void) pbtTxPar;
   (void) pbtRxPar;
-  unsigned int i;
+  uint16_t i;
   uint8_t sz;
 
   // Sorry, no arbitrary parity bits support for now
@@ -1253,7 +1248,7 @@ pn53x_initiator_transceive_bits_timed (nfc_device_t * pnd, const byte_t * pbtTx,
   // our PN53x timer saturates after 4.8ms so this function shouldn't be used for
   // responses coming very late anyway.
   // Ideally we should implement a real timer here too but looping a few times is good enough.
-  for (i=0; i<(3 *(__timer_prescaler * 2 + 1)); i++) {
+  for (i=0; i<(3 *(CHIP_DATA (pnd)->timer_prescaler * 2 + 1)); i++) {
     pn53x_read_register (pnd, PN53X_REG_CIU_FIFOLevel, &sz);
     if (sz > 0)
       break;
@@ -1298,7 +1293,7 @@ bool
 pn53x_initiator_transceive_bytes_timed (nfc_device_t * pnd, const byte_t * pbtTx, const size_t szTx, byte_t * pbtRx,
                                         size_t * pszRx, uint32_t * cycles)
 {
-  unsigned int i;
+  uint16_t i;
   uint8_t sz;
 
   // We can not just send bytes without parity while the PN53X expects we handled them
@@ -1348,7 +1343,7 @@ pn53x_initiator_transceive_bytes_timed (nfc_device_t * pnd, const byte_t * pbtTx
   // our PN53x timer saturates after 4.8ms so this function shouldn't be used for
   // responses coming very late anyway.
   // Ideally we should implement a real timer here too but looping a few times is good enough.
-  for (i=0; i<(3 *(__timer_prescaler * 2 + 1)); i++) {
+  for (i=0; i<(3 *(CHIP_DATA (pnd)->timer_prescaler * 2 + 1)); i++) {
     pn53x_read_register (pnd, PN53X_REG_CIU_FIFOLevel, &sz);
     if (sz > 0)
       break;
diff --git a/libnfc/chips/pn53x.h b/libnfc/chips/pn53x.h
index cc6b775..8e3468e 100644
--- a/libnfc/chips/pn53x.h
+++ b/libnfc/chips/pn53x.h
@@ -159,6 +159,8 @@ struct pn53x_data {
   uint8_t ui8LastCommand;
 /** Interframe timer correction */
   int16_t timer_correction;
+/** Timer prescaler */
+  uint16_t timer_prescaler;
 /** WriteBack cache */
   uint8_t wb_data[PN53X_CACHE_REGISTER_SIZE];
   uint8_t wb_mask[PN53X_CACHE_REGISTER_SIZE];