Texas Instruments MSP430x1xx - Manual (Page 173)

Timer_A UART
10-33
Timer_A
10.6.4.4 Timing Limits
With the TAIV register and the previous software, the shortest repetitive time
distance t
CRmin
between two events using a compare register is:
t
CRmin
= t
taskmax
+ 16
×
t
cycle
With: t
taskmax
Maximum (worst case) time to perform the task during the
interrupt routine (for example, incrementing a counter)
t
cycle
Cycle time of the system frequency MCLK
The shortest repetitive time distance t
CLmin
between two events using a
capture register is:
t
CLmin
= t
taskmax
+ 16 x t
cycle
10.7 Timer_A UART
The Timer_A is uniquely capable of implementing a UART function, with the
following features:
- Automatic start-bit detection – even from ultralow-power modes
- Hardware baud-rate generation
- Hardware latching of RXD and TXD data
- Baud rates of 75 to 115,200 baud
- Full-duplex operation
This UART implementation is different from other microcontroller implementa-
tions where a UART may be implemented with general-purpose I/O and manu-
al bit manipulation via software polling. Those implementations require great
CPU overhead and therefore increase power consumption and decrease the
usability of the CPU.
The transmit feature uses one compare function to shift data through the
output unit to the selected pin. The baud rate is ensured by reconfiguring the
compare data with each interrupt.