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CHAPTER 7 UART
446
Preliminary User’s Manual S14767EJ1V0UM00
7.3 UART Registers
This controller uses the NEC NA16550L Mega-Function as its internal UART. This UART is functionally identical to
the National Semiconductor NS16550D. Refer to the NEC “User’s Manual. Mega FunctionNA16550L” for more
information and programming details.
7.3.1 UART Receiver data Buffer Register (UARTRBR) (80H, DLAB = 0, R)
This register holds receive data. It is only accessed when the Divisor Latch Access bit(DLAB) is cleared in the
UARTLCR.
Bits
Field
Description
7:0
UDATA
UART data (read only) when DLAB = 0.
31:8
Reserved
Hardwired to 0.
7.3.2 UART Interrupt Enable Register (UARTIER) (84H, DLAB = 1, R/W)
This register is used to enable UART interrupts. It is only accessed when the Divisor Latch Access bit (DLAB) is set
in the UARTLCR. The UARTIM bit2 in Interrupt Mask Register “IMR” is a global enable for interrupt sources enabled
by this register.
Bits
Field
Description
0
ERBFI
UART Receive data Buffer Full Interrupt
1 = Enable receive-data-available interrupt
0 = Disable such interrupts
Receive data-Buffer-Full state reported to UARTLSR
1
ERBEI
UART Transmitter Buffer empty Interrupt
1 = Enable Transmitter Buffer empty interrupt
0 = Disable such interrupts
Transmitter Buffer empty state reported to UARTLSR
2
ERBLI
UART Line status Interrupts
1 = Enable Line status error interrupt
0 = Disable such interrupts
Line status error interrupt state reported to UARTLSR
3
ERBMI
UART Modem status Interrupts
1 = Enable Modem status change interrupt
0 = Disable such interrupts
Modem status changes are reported to UARTMSR
31:4
Reserved
Hardwired to 0.