AT83EC5123 ATMEL Corporation, AT83EC5123 Datasheet - Page 93

• Manufacturer Part Number: AT83EC5123
• Description: (AT8xx512x) Smart Card Reader ICs
• Manufacturer: ATMEL Corporation

Baud Rate Selection (Mode 0)
Asynchronous Modes
(Modes 1, 2 and 3)
Figure 56. Serial I/O Port Block Diagram (Modes 1, 2 and 3)
Mode 1
4202B–SCR–07/03
CLOCK
CLOCK
IBRG
CK_
T1
SI
SCON.4
SM2
In mode 0, baud rate can be either fixed or variable.
As shown in Figure 54, the selection is done using M0SRC bit in BDRCON register.
Figure 55 gives the baud rate calculation formulas for each baud rate source.
Figure 54. Baud Rate Source Selection (Mode 0)
Figure 55. Baud Rate Formulas (Mode 0)
The Serial Port has one 8-bit and two 9-bit asynchronous modes of operation. Figure 56
shows the Serial Port block diagram in such asynchronous modes.
Mode 1 is a full-duplex, asynchronous mode. The data frame (see Figure 57) consists of
10 bits: one start, eight data bits and one stop bit. Serial data is transmitted on the TXD
pin and received on the RXD pin. When a data is received, the stop bit is read in the
RB8 bit in SCON register.
SCON.6
M3 M2 M1 M0
SM1
Mode Decoder
Mode & Clock
Controller
Baud_Rate =
SCON.1
a. Fixed Formula
TI
SCON.7
SM0
SCON.0
RI
F
CLOCK
CK_SI
IBRG
6
CK_
SI
/ 6
SCON.3
SBUF Tx SR
TB8
SBUF Rx
BDRCON.0
M0SRC
Rx SR
0
1
Baud_Rate =
BRL = 256 -
b. Variable Formula
SCON.2
RB8
To Serial Port
AT8xC5122/23
6
6
(1-SPD)
(1-SPD)
2
2
SMOD1
SMOD1
32 Baud_Rate
32 (256 -BRL)
TXD
RXD
F
F
CK_SI
CK_SI
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