P R O G R A M M E R  21 Pins  ˛  Selects  the  number  of  pins  for  SX18  (20)/28.  Set  it  to  the  correct  value,  according  to  your  target microcontroller. Reset Time ˛ Delay Reset Timer (DRT) timeout period (SX48/52 only). The SX18 (20)/28 devices have a fixed startup time of 18 ms when the wakeup reset occurs. The SX48/52 devices have a programmable startup time. Timeout period can be one of the following: 0.06 ms, 18 ms, 60 ms, 960 ms. BrownOut ˛ Set the Brown Out Reset threshold voltage. When the supply voltage to the SX device drops below a specified value but remains above zero volts, it is called as ´brown-outµ condition. The SX device has a brownout detection circuit that puts the device into the reset state when the brownout occurs, and allows the device  to  re-start  when  the  brownout  condition  ends.  This  feature  prevents  the  device  from  producing abnormal results when the supply voltage falls to unreliable levels. The brownout threshold voltage can be programmed to the following three levels ˛ 4.2 V, 2.6 V, 2.2 V. If the supply voltage drops below this level but remains above zero, the brownout circuit holds the SX device in the reset state. When the voltage rises above this  threshold,  the  device  start  operating  again,  starting  at  the  reset  address.  Fine-tuning  of  the  brownout threshold voltage can be done with brownout trim bits. If the brownout detection circuit disabled, device will still operate below the brownout threshold voltage, but will produce unreliable results if the supply voltage falls too low. Turbo mode ˛ SX18 (20)/28 only option. If set, the instruction clock rate is equal to the oscillator clock rate. If cleared, the instruction rate operates at one-fourth the oscillator clock rate. See also &hapter 4, option 7). Watchdog  Timer ˛ Enable Watchdog Timer. If set, a watchdog timeout occurs when the watchdog timer overflows.  This  feature  provides  an  escape  mechanism  from  an  infinite  loop  or  other  abnormal  program conditions. When a watchdog timeout occurs, it resets the device just like assertion of the M&LR input. The watchdog oscillator has a nominal frequency of 14 kHz; at this rate 8-bit watchdog timer overflows in 18 ms. the watchdog period can be increased under program control up to 2.34 s with OPTION register. &ode Protect ˛ &ode Protection. If set, the program code and configuration registers read back as scrambled data. This prevents reverse engineering of your proprietary code and configuration options. Add/Sub with & ˛ &arry bit Input. If set, carry bit will be add into all addition operations (ADD fr, W means fr fr+W+&); and to subtract the complement of the carry bit from all subtraction operations (SUB fr, W means fr fr-W-/&). If clear, carry bit will be ignored as an input for addition and subtraction operations. Input Sync ˛ Synchronous Input Mode. If set, input signals will be synchronized with internal clock through two internal flip-flops. If clear, input signals will go directly to the port inputs. IFBD ˛ Internal Feedback Disable. External oscillator mode only. If set, the crystal/oscillator can rely on the internal feedback resistor between the OS&1 and OS&2 pins. If clear, an external feedback resistor is required between the OS&1 and OS&2 pins. Option Extend ˛ OPTION register Extension and Stack Extension, SX18 (20)/28 only option. If set, enable programmability of bit 6 and 7 in the OPTION register, the RTW and RTE_IE bits and to extend the stack