mcs7840 MosChip, mcs7840 Datasheet - Page 17

• Manufacturer Part Number: mcs7840
• Description: Usb-2.0 To Four Serial Ports
• Manufacturer: MosChip

Rev.
Modem Status Register (MSR):
This register provides the status of the modem control lines to CPU.
Register:
Description:
Offset:
Permissions:
Access Condition:
Default Value:
1.2
Bit[7]
DCD
Bit
0
1
2
3
4
5
6
7
MSR
Modem Status Register
6
Read
0x00
Bit[6]
Trailing Edge of RI
RI
Description
Delta DCD
Delta DSR
Delta CTS
DSR
DCD
CTS
RI
Bit[5]
DSR
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Logic 0:
Logic 1:
Bit[4]
CTS
the last time the MSR was read
the last time the MSR was read
to high since the last time the MSR was read
the last time the MSR was read
No change in the CTS signal
Indicates that the CTS input has changed since
No change in the DSR signal
Indicates that the DSR input has changed since
No change in the RI signal
Indicates that the RI input has changed from low
No change in the DCD signal
Indicates that the DCD input has changed since
CTS# line is 1
CTS# line is 0
DSR# line is 1
DSR# line is 0
RI# line is 1
RI# line is 0
DCD# line is 1
DCD# line is 0
ΔDCD
Bit[3]
USB-2.0 to Four Serial Ports
Operation
Bit[2]
Teri
MCS7840
ΔDSR
Bit[1]
ΔCTS
Bit[0]
Page 17