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ST16C1450/51

REV. 4.2.0

2.97V TO 5.5V UART

21

CTS# (active high, logical 1). Normally this bit is the compliment of the CTS# input. In the loopback mode, this

bit is equivalent to bit-1 in the MCR register. The CTS# input may be used as a general purpose input when the

modem interface is not used.

MSR[5]: DSR Input Status

DSR# (active high, logical 1). Normally this bit is the compliment of the DSR# input. In the loopback mode, this

bit is equivalent to bit-0 in the MCR register. The DSR# input may be used as a general purpose input when the

modem interface is not used.

MSR[6]: RI Input Status

RI# (active high, logical 1). Normally this bit is the compliment of the RI# input. In the loopback mode this bit is

equivalent to bit-2 in the MCR register. The RI# input may be used as a general purpose input when the

modem interface is not used.

MSR[7]: CD Input Status

CD# (active high, logical 1). Normally this bit is the compliment of the CD# input. In the loopback mode this bit

is equivalent to bit-3 in the MCR register. The CD# input may be used as a general purpose input when the

modem interface is not used.

4.9

Scratch Pad Register (SPR) - Read/Write

This is a 8-bit general purpose register for the user to store temporary data. The content of this register is

preserved during sleep mode but becomes 0xFF (default) after a reset or a power off-on cycle.

REGISTERS

RESET STATE

DLL

Bits 7-0 = 0xXX

DLM

Bits 7-0 = 0xXX

RHR

Bits 7-0 = 0xXX

THR

Bits 7-0 = 0xXX

IER

Bits 7-0 = 0x00

ISR

Bits 7-0 = 0x01

LCR

Bits 7-0 = 0x00

MCR

Bits 7-0 = 0x00

LSR

Bits 7-0 = 0x60

MSR

Bits 3-0 = Logic 0

Bits 7-4 = Logic levels of the inputs inverted

SPR

Bits 7-0 = 0xFF

I/O SIGNALS

RESET STATE

TX

Logic 1

RTS#

Logic 1

DTR#

Logic 1

RST

Logic 1

INT

Three-State Condition