MMUART Peripherals
UG0331 User Guide Revision 15.0
474
13.2.3.2 MMUART Reset
MMUART resets to zero on power-up and is held in reset until it is enabled. An option is provided under
software control to reset the MMUART by writing to bit 7 or bit 8 of the SOFT_RESET_CR, located in the
SYSREG block. At power-up, the reset signals are asserted 1. This keeps MMUART peripherals in a
reset state. MMUART peripheral becomes active when the bit is set to 0, as mentioned in the following
table.
13.2.3.3 Clock Requirements
The MMUART_0 and MMUART _1 peripherals are clocked by APB_0_CLK on APB bus 0 and
APB_1_CLK on APB bus 1. These clocks are derived from the main MSS clock M3_CLK. Each APB
clock can be programmed individually as M3_CLK divided by 1, 2, 4, or 8. Refer to the
UG0449: SmartFusion2 and IGLOO2 Clocking Resources User Guide
for more information on clocks.
The baud rate generator block receives the input from APB clock and divides by the value of the Baud
Rate Registers (
,
). The result is then divided further by 16 to produce the integer
baud rate. The resultant signal is the BAUDOUT signal. The MMUART also has a fractional baud rate
generation capability. These features are described in detail in
13.2.3.4 Interrupts
There is one interrupt signal from each MMUART peripheral. The MMUART_0_INT signal is generated
by MMUART_0 and is mapped to INTISR[10] in the Cortex-M3 processor nested vectored interrupt
controller (NVIC). The MMUART_1_INT signal is generated by MMUART_1 and is mapped to
INTISR[11] in the Cortex-M3 processor NVIC. Both interrupt enable bits within NVIC-INTISR[10] and
INTISR[11] correspond to bit locations 10 and 11. MMUART interrupts can be enabled by setting the
appropriate bits in the IER register while the divisor latch access bit of
Ensure the clearing of the appropriate bit in the IER interrupt service routine to prevent a re-assertion of
the interrupt. It should be noted that there is currently no priority scheme to interrupt within the MMUART
peripheral.
13.2.4
Details of Operation
This sub-section provides functional description of MMURAT internal components and different modes of
MMUART operation.
13.2.4.1 Baud Rate Generation
The baud rate generator contains free-running counters that generate the internal clocks. The design
utilizes an asynchronous baud rate generation circuit and also allows for synchronous Slave and Master
modes.
Table 465 •
Soft Reset Bit Definition for the MMUART_x
Bit
Numb
er
Name
R/W
Reset
Value Description
8
MMUART1_SOFTRESET
R/W
0x1
Controls reset input to MMUART_1
0: Release MMUART_1 from reset
1: Keep MMUART_1 in reset (reset value)
7
MMUART0_SOFTRESET
R/W
0x1
Controls reset input to MMUART_0
0: Release MMUART_0 from reset
1: Keep MMUART_0 in reset (reset value)
Содержание SmartFusion2 MSS
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