W83877TF Datasheet, PDF (6/154 Pages) Winbond – I/O chip disk drive adapter

W83877TF
Bit 3: NSER. This bit is set to a logical 1 to indicate that the received data have no stop bit. In 16550
mode, it indicates the same condition for the data on top of the FIFO. When the CPU reads
USR, it will clear this bit to a logical 0.
Bit 2: PBER. This bit is set to a logical 1 to indicate that the parity bit of received data is wrong. In
16550 mode, it indicates the same condition for the data on top of the FIFO. When the CPU
reads USR, it will clear this bit to a logical 0.
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.
3.2.3 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 a 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.
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Publication Release Date: March 1998
Version 0.61