SFR Definitions

MSINT (Milliseconds Interrupt, Address FAH): This SFR can be set to cause an interrupt to occur after the specified number of milliseconds. This as- sumes that the millisecond registers FCH and FDH are set to generate a cycle every millisecond. The precise frequency at which MSINT will cause an inter- rupt depends on the system clock and the value of the MSECH, MSECL, and MSINT SFRs.

USEC (Microsecond Register, Address FBH): This SFR is divided into the clock speed to determine the timing of 1ms. This value is used for program- ming flash memory. The value in USEC, taken together with the low four bits of FTCON, should produce a timing of 30s to 40s, which is used for flash write operations.

MSECL/MSECH (Millisecond Low/High Registers, Addresses FCH/FDH):

These two SFRs, together, are used by the system to determine how long a millisecond is. This value is used for erasing flash memory, millisecond interrupt, second interrupt, and watchdog time. Although it is named Millisecond Low/High, the clock speed and the value placed in these registers will determine the exact length of time measured.

HMSEC (Hundred Millisecond Clock, Address FEH): This SFR is used to create a 100ms clock based on the MSECL/MSECH SFRs. However, the ex- act frequency generated by this SFR will depend on the system clock, the val- ue of MSECL/MSECH, and the value placed in this register.

WDTCON (Watchdog Control, Address FFH): The WDTCON SFR is used to enable, disable, and reset the watchdog timer. Once enabled, this SFR must be periodically reset in order to prevent the system from resetting.

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Texas Instruments MSC1210 manual SFR Definitions