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UART emulator CPU load and footprint

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UART emulator CPU load and footprint

The UART emulator uses the CPU for several tasks such as data formatting, DMA interrupt

handling both for transmission and reception and EXTI interrupt handling for reception.

4.1

CPU load

The CPU load depends on whether the transmit or receive process is active. When UART

full-duplex mode is active, the CPU load is increased. Refer to Table 5 for an example.

The software settings used to obtain the results given in Table 5 are the following:

•

System clock: 84 MHz

•

Toolchain: MDK-ARM V5.14, optimization level3(-O3) for size

•

Word length: 8 bits

•

One stop bit

•

No parity.

4.2

UART emulator memory footprint

Table 6 gives an estimate of the code size required by the UART emulator software

compiled with MDK-ARM V5.14, optimization level3(-O3) for size.

Table 5. UART CPU Load

Baudrate (bps)

Transmission

Reception

Load CPU (%)

MIPS

Load CPU (%)

MIPS

4800

2.4

2

4

3

9600

5

4

8.8

7

115200

6

5

9

7.5

Table 6. UART memory footprint

Flash memory footprint (bytes)

RAM footprint (bytes)

2872

400