AT89C5122 ATMEL [ATMEL Corporation], AT89C5122 Datasheet - Page 133

• Manufacturer Part Number: AT89C5122
• Description: MICROCONTROLLER WITH USB AND SMART CARD READER INTERFACES
• Manufacturer: ATMEL [ATMEL Corporation]

Baud Rate Selection
(Modes 1 and 3)
4202D–SCR–06/05
CLOCK
CLOCK
IBRG
T1
BDRCON.2
RBCK
In modes 1 and 3, the Baud Rate is derived either from the Timer 1 or the Internal Baud
Rate Generator and allows different baud rate in reception and transmission.
As shown in Figure 79 the selection is done using RBCK and TBCK bits in BDRCON
register.
Figure 80 gives the baud rate calculation formulas for each baud rate source while
Table 76 details Internal Baud Rate Generator configuration for different peripheral
clock frequencies and giving baud rates closer to the standard baud rates.
Figure 79. Baud Rate Source Selection (Modes 1 and 3)
Figure 80. Baud Rate Formulas (Modes 1 and 3)
0
1
Baud_Rate =
BRL = 256 -
/ 16
a. IBRG Formula
6
6
(1-SPD)
(1-SPD)
2
2
To serial
reception Port
SMOD1
SMOD1
⋅ 32 ⋅ (256 -BRL)
⋅ 32 ⋅ Baud_Rate
⋅
⋅
F
F
CK_SI
CK_SI
CLOCK
CLOCK
IBRG
T1
BDRCON.3
TBCK
0
1
Baud_Rate =
TH1 = 256 -
/ 16
b. T1 Formula
6 ⋅ 32 ⋅ (256 -TH1)
192 ⋅ Baud_Rate
2
2
To serial
transmission Port
SMOD1
SMOD1
⋅
⋅
F
F
CK_T1
CK_T1
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