w83977ctf Winbond Electronics Corp America, w83977ctf Datasheet - Page 58

• Manufacturer Part Number: w83977ctf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

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.
Bit 4: When this bit is set to a logical 1, the UART enters diagnostic mode by an internal loopback, as
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#.
3.2.4 Handshake Status Register (HSR) (Read/Write)
This register reflects the current state of four input pins for handshake peripherals such as a modem,
and records changes on these pins.
follows:
(1) SOUT is forced to logical 1, and SIN is isolated from the communication link instead of the
(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 is internally connected to the modem control input DCD#.
connected to the modem control input RI#.
TSR.
(bit 0 of HCR)
RI#and IRQ enable ( bit 3 of HCR)
Aside from the above connections, the UART operates normally. This method allows the
CPU to test the UART in a convenient way.
7
0
0
DSR#, RTS ( bit 1 of HCR)
6
5
0
4
3
2
-49 -
DCD#.
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
Publication Release Date: March 1999
W83977EF/ CTF
PRELIMINARY
Revision A1