ST16C654CJ68 EXAR [Exar Corporation], ST16C654CJ68 Datasheet - Page 31

• Manufacturer Part Number: ST16C654CJ68
• Description: QUAD UART WITH 64-BYTE FIFO AND INFRARED (IrDA) ENCODER/DECODER
• Manufacturer: EXAR [Exar Corporation]

break indication is in the current FIFO data. This bit is
cleared when LSR register is read.
Modem Status Register (MSR)
This register provides the current state of the control
interface signals from the modem, or other peripheral
device that the 654 is connected to. Four bits of this
register are used to indicate the changed information.
These bits are set to a logic 1 whenever a control input
from the modem changes state. These bits are set to
a logic 0 whenever the CPU reads this register.
MSR BIT-0:
Logic 0 = No -CTS Change (normal default condition)
Logic 1 = The -CTS input to the 654 has changed state
since the last time it was read. A modem Status
Interrupt will be generated.
MSR BIT-1:
Logic 0 = No -DSR Change. (normal default condition)
Logic 1 = The -DSR input to the 654 has changed state
since the last time it was read. A modem Status
Interrupt will be generated.
MSR BIT-2:
Logic 0 = No -RI Change. (normal default condition)
Logic 1 = The -RI input to the 654 has changed from
a logic 0 to a logic 1. A modem Status Interrupt will be
generated.
MSR BIT-3:
Logic 0 = No -CD Change. (normal default condition)
Logic 1 = Indicates that the -CD input to the has
changed state since the last time it was read. A
modem Status Interrupt will be generated.
MSR BIT-4:
-CTS functions as hardware flow control signal input if
it is enabled via EFR bit-7. The transmit holding
register flow control is enabled/disabled by MSR bit-4.
Flow control (when enabled) allows the starting and
stopping the transmissions based on the external
modem -CTS signal. A logic 1 at the -CTS pin will stop
654 transmissions as soon as current character has
finished transmission.
Rev. 4.10
5-95
Normally MSR bit-4 bit is the compliment of the -CTS
input. However in the loopback mode, this bit is
equivalent to the RTS bit in the MCR register.
MSR BIT-5:
DSR (active high, logical 1). Normally this bit is the
compliment of the -DSR input. In the loopback mode,
this bit is equivalent to the DTR bit in the MCR register.
MSR BIT-6:
RI (active high, logical 1). Normally this bit is the
compliment of the -RI input. In the loopback mode this
bit is equivalent to the OP1 bit in the MCR register.
MSR BIT-7:
CD (active high, logical 1). Normally this bit is the
compliment of the -CD input. In the loopback mode
this bit is equivalent to the OP2 bit in the MCR register.
Scratchpad Register (SPR)
The ST16C654 provides a temporary data register to
store 8 bits of user information.
Enhanced Feature Register (EFR)
Enhanced features are enabled or disabled using this
register.
Bits-0 through 4 provide single or dual character
software flow control selection. When the Xon1 and
Xon2 and/or Xoff1 and Xoff2 modes are selected, the
double 8-bit words are concatenated into two sequen-
tial characters.
EFR BIT 0-3: (logic 0 or cleared is the default condi-
tion)
Combinations of software flow control can be selected
by programming these bits.
ST16C654/654D