W83877 Winbond Electronics Corp America, W83877 Datasheet - Page 46

• Manufacturer Part Number: W83877
• Description: Winbond I/O
• Manufacturer: Winbond Electronics Corp America

Bit 1: OER. This bit is set to a logical 1 to indicate received data have been overwritten by the next
Bit 0: RDR. This bit is set to a logical 1 to indicate received data are ready to be read by the CPU in
4.2.3 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.
Bit 4: When this bit is set to a logical 1, the UART enters diagnostic mode by an internal loopback, as
the
Bit 3: The UART interrupt output is enabled by setting this bit to a logic 1. In the diagnostic mode this
Bit 2: This bit is used only in the diagnostic mode. In the diagnostic mode this bit is internally
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 .
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.
the RBR or FIFO. After no data are left in the RBR or FIFO, the bit will be reset to a logical 0.
follows:
bit is internally connected to the modem control input DCD .
connected to the modem control input RI .
(1) SOUT is forced to a logical 1, and SIN is isolated from the communication link instead of
(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
TSR.
(bit 0 of HCR)
Aside from the above connections, the UART operates normally. This method allows the
CPU to test the UART in a convenient way.
RI and IRQ enable ( bit 3 of HCR)
7
0
0
6
DSR, RTS ( bit 1 of HCR)
5
0
4
3
2
DCD .
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1
0
CTS, Loopback RI input ( bit 2 of HCR)
Data terminal ready (DTR)
Request to send (RTS)
Loopback RI input
IRQ enable
Internal loopback enable
W83877F