W83L517D_05 Datasheet, PDF (49/133 Pages) Winbond – LPC I/O for Notebook

W83L517D/W83L517D-F
Bit 1: OER. This bit is set to a logical 1 to indicate received data have been overwritten by the next
received data before they were read by the CPU. In 16550 mode, it indicates the same condition
instead of FIFO full. When the CPU reads USR, it will clear this bit to a logical 0.
Bit 0: RDR. This bit is set to a logical 1 to indicate received data are ready to be read by the CPU in
the RBR or FIFO. After no data are left in the RBR or FIFO, the bit will be reset to a logical 0.
7.2.3 Handshake Control Register (HCR) (Read/Write)
This register controls the pins of the UART used for handshaking peripherals such as modem, and
controls the diagnostic mode of the UART.
7 6 5 4 32
00 0
10
Data terminal ready (DTR)
Request to send (RTS)
Loopback RI input
IRQ enable
Internal loopback enable
Bit 4: When this bit is set to a logical 1, the UART enters diagnostic mode by an internal loopback, as
follows:
(1) SOUT is forced to logical 1, and SIN is isolated from the communication link instead of the
TSR.
(2) Modem output pins are set to their inactive state.
(3) Modem input pins are isolated from the communication link and connect internally as DTR
(bit 0 of HCR) → DSR, RTS ( bit 1 of HCR) → CTS, Loopback RI input ( bit 2 of HCR) → RI
and IRQ enable ( bit 3 of HCR) → DCD .
Aside from the above connections, the UART operates normally. This method allows the CPU
to test the UART in a convenient way.
Bit 3: The UART interrupt output is enabled by setting this bit to a logic 1. In the diagnostic mode this
bit is internally connected to the modem control input DCD .
Bit 2: This bit is used only in the diagnostic mode. In the diagnostic mode this bit is internally
connected to the modem control input RI .
Bit 1: This bit controls the RTS output. The value of this bit is inverted and output to RTS .
Bit 0: This bit controls the DTR output. The value of this bit is inverted and output to DTR .
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Publication Release Date: May 23, 2005
Revision 1.0