RC56D, RC336D, and RC144D Modem Device Sets Designer’s Guide
4-2
Conexant
1154
Table 4-1. Parallel Interface Registers
Register
Register
Bit No.
No.
Name
7
6
5
4
3
2
1
0
7
Scratch Register (SCR)
Scratch Register
6
Modem Status Register
(MSR)
Data Carrier
Detect
(DCD)
Ring
Indicator
(RI)
Data Set
Ready
(DSR)
Clear to
Send
(CTS)
Delta Data
Carrier
Detect
(DDCD)
Trailing
Edge of
Ring
Indicator
(TERI)
Delta Data
Set Ready
(DDSR)
Delta Clear
to Send
(DCTS)
5
Line Status Register (LSR)
RX FIFO
Error
Transmitter
Empty
(TEMT)
Transmitter
Buffer
Register
Empty
(THRE)
Break
Interrupt
(BI)
Framing
Error
(FE)
Parity
Error
(PE)
Overrun
Error
(OE)
Receiver
Data Ready
(DR)
4
Modem Control Register
(MCR)
0
0
0
Local
Loopback
Out 2
Out 1
Request to
Send
(RTS)
Data
Terminal
Ready
(DTR)
3
Line Control Register
(LCR)
Divisor
Latch
Access Bit
(DLAB)
Set Break
Stick Parity Even Parity
Select
(EPS)
Parity
Enable
(PEN)
Number of
Stop Bits
(STB)
Word
Length
Select Bit 1
(WLS1)
Word
Length
Select Bit 0
(WLS0)
2
Interrupt Identify Register
(IIR) (Read Only)
FIFOs
Enabled
FIFOs
Enabled
0
0
Pending
Interrupt ID
Bit 2
Pending
Interrupt ID
Bit 1
Pending
Interrupt ID
Bit 0
“0" if
Interrupt
Pending
2
FIFO Control Register
(FCR) (Write Only)
Receiver
Trigger
MSB
Receiver
Trigger
LSB
Reserved
Reserved
DMA Mode
Select
TX FIFO
Reset
RX FIFO
Reset
FIFO
Enable
1
(DLAB = 0)
Interrupt Enable Register
(IER)
0
0
0
0
Enable
Modem
Status
Interrupt
(EDSSI)
Enable
Receiver
Line Status
Interrupt
(ELSI)
Enable
Transmitter
Holding
Register
Empty
Interrupt
(ETBEI)
Enable
Received
Data
Available
Interrupt
(ERBFI)
0
(DLAB = 0)
Transmitter Buffer Register
(THR)
Transmitter FIFO Buffer Register (Write Only)
0
(DLAB = 0)
Receiver Buffer Register
(RBR)
Receiver FIFO Buffer Register (Read Only)
1
(DLAB = 1)
Divisor Latch MSB
Register (DLM)
Divisor Latch MSB
0
(DLAB = 1)
Divisor Latch LSB Register
(DLL)
Divisor Latch LSB
Summary of Contents for RC144D
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