A96G140/A96G148/A96A148 User’s manual
15. USI
159
Transmitter consists of a single write buffer, a serial shift register, parity generator and control logic for
handling different serial frame formats. A write buffer allows continuous transfer of data without any
delay between frames.
Receiver is the most complex part of the UART module due to its clock and data recovery units. The
recovery unit is used for asynchronous data reception. In addition to the recovery unit, the receiver
includes a parity checker, a shift register, a two-level receive FIFO (USInDR) and control logic. The
receiver supports the same frame formats as the transmitter and can detect frame error, data overrun
and parity errors.
15.2
USIn UART block diagram
RXDn
Rx
Control
Clock
Recovery
Receive Shift Register
(RXSR)
Data
Recovery
DORn/PEn/FEn
Checker
USInDR[0], USInRX8[0], (Rx)
USInDR[1], USInRX8[1], (Rx)
TXDn
Tx
Control
Stop bit
Generator
Parity
Generator
Transmit Shift Register
(TXSR)
USInDR, USInTX8, (Tx)
USInP[1:0]
M
U
X
LOOPSn
TXCn
TXCIEn
DRIEn
DREn
Empty signal
To interrupt
block
INT_ACK
Clear
RXCn
RXCIEn
WAKEIEn
WAKEn
At Stop mode
To interrupt
block
SCLK
(fx: System clock)
Low level
detector
2
USInS[2:0]
3
USInS[2:0]
3
TXEn
RXEn
DBLSn
USInSB
Baud Rate Generator
USInBD
I
N
T
E
R
N
A
L
B
U
S
L
I
N
E
SCKn
ACK
Control
Clock
Sync Logic
Master
USInMS[1:0]
M
U
X
M
U
X
USInMS[1:0]
USInMS[1:0]
2
2
2
Figure 84. USIn USART Block Diagram (n = 0 and 1)