Laptop User Manual

S3C2440A RISC MICROPROCESSOR UART

11-19

UART MODEM STATUS REGISTER

There are two UART modem status registers including UMSTAT0, UMSTAT1 in the UART block.

UMSTAT0 0x5000001C R UART channel 0 Modem status register 0x0

UMSTAT1 0x5000401C R UART channel 1 Modem status register 0x0

Reserved 0x5000801C - Reserved Undef

UMSTAT0 Bit Description Initial State

Delta CTS [4] Indicate that the nCTS input to the S3C2440A has changed

state since the last time it was read by CPU.

(Refer to Figure 11-8.)

0 = Has not changed

1 = Has changed

Reserved [3:1] 0

Clear to Send [0] 0 = CTS signal is not activated (nCTS pin is high)

1 = CTS signal is activated (nCTS pin is low)

nCTS

Delta CTS

Read_UMSTAT

Figure 11-7. nCTS and Delta CTS Timing Diagram