XR16M564 Datasheet, PDF (16/55 Pages) Exar Corporation – 1.62V TO 3.63V QUAD UART WITH 32-BYTE FIFO

XR16M564/564D
1.62V TO 3.63V QUAD UART WITH 32-BYTE FIFO
REV. 1.0.0
2.9.2 Transmitter Operation in non-FIFO Mode
The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the
data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled
by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty.
FIGURE 7. TRANSMITTER OPERATION IN NON-FIFO MODE
Data
Byte
Transmit
Holding
Register
(THR)
16X or 8X or 4X
Clock
( DLD[5:4] )
Transmit Shift Register (TSR)
THR Interrupt (ISR bit-1)
Enabled by IER bit-1
M
L
S
S
B
B
TXNOFIFO1
2.9.3 Transmitter Operation in FIFO Mode
The host may fill the transmit FIFO with up to 32 bytes of transmit data. The THR empty flag (LSR bit-5) is set
whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the
FIFO becomes empty. The transmit empty interrupt is enabled by IER bit-1. The TSR flag (LSR bit-6) is set
when TSR/FIFO becomes empty.
FIGURE 8. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE
Transmit
Data Byte
Auto CTS Flow Control (CTS# pin)
Flow Control Characters
(Xoff1/2 and Xon1/2 Reg.)
Auto Software Flow Control
Transmit
FIFO
THR Interrupt (ISR bit-1) falls
below the programmed Trigger
Level and then when becomes
empty. FIFO is Enabled by FCR
bit-0=1
16X or 8X or 4X Clock
(DLD[5:4])
Transmit Data Shift Register
(TSR)
TX FIFO 1
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