Rainbow-electronics AT89C5122 Bedienungsanleitung PDF herunterladen (Seite 134)

134

AT8xC5122/23

4202E–SCR–06/06

Baud Rate Selection (Mode 2) In mode 2, the baud rate can only be programmed to two fixed values: 1/16 or 1/32 of

the peripheral clock frequency.

As shown in Figure 81 the selection is done using SMOD1 bit in PCON register.

Figure 82 gives the baud rate calculation formula depending on the selection.

Figure 81. Baud Rate Generator Selection (Mode 2)

Figure 82. Baud Rate Formula (Mode 2)

For mode 0 for UART, thanks to the bit M0SRC located in BDRCON register (Table 82)

Table 76. Internal Baud Rate Generator Value

Baud Rate

CK_IDLE

= 4 MHz F

CK_IDLE

= 8 MHz F

CK_IDLE

= 9.6 MHz

SPD SMOD1 BRL Error% SPD SMOD1 BRL Error% SPD SMOD1 BRL Error%

115200 1 1 254 8.51 1 1 252 8.51 1 1 251 4.17

57600 1 1 252 8.51 1 1 247 3.55 1 1 246 4.17

38400 1 1 249 6.99 1 1 243 0.16 1 1 240 2.34

19200 1 1 243 0.16 1 1 230 0.16 1 1 225 0.81

9600 1 1 230 0.16 1 1 204 0.16 1 1 194 0.81

4800 1 1 204 0.16 1 1 152 0.16 1 1 131 0.00

Baud Rate

CK_IDLE

= 12 MHz F

CK_IDLE

= 16 MHz F

CK_IDLE

= 24 MHz

SPD SMOD1 BRL Error% SPD SMOD1 BRL Error% SPD SMOD1 BRL Error%

115200 1 1 249 6.99 1 1 247 3.55 1 1 243 0.16

57600 1 1 243 0.16 1 1 239 2.12 1 1 230 0.16

38400 1 1 236 2.34 1 1 230 0.16 1 1 217 0.16

19200 1 1 217 0.16 1 1 204 0.16 1 1 178 0.16

9600 1 1 178 0.16 1 1 152 0.16 1 1 100 0.16

4800 1 1 100 0.16 1 1 48 0.16 1 1 N/A N/A

SMOD1

PCON.7

CK_

/ 2

³ 16

To Serial Por

Baud_Rate =

⋅ F

CK_SI

1 2 ... 129 130 131 132 133 134 135 136 137 138 139 ... 212 213

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