ADUC7021 datasheet(64/92 Pages) AD

64 / 92 page

ADuC7019/20/21/22/24/25/26/27

Rev. A | Page 64 of 92

COMCON1 Register

Name

Address

Default Value

Access

COMCON1

0xFFFF0710

0x00

R/W

COMCON1 is the modem control register.

Table 51. COMCON1 MMR Bit Descriptions

Bit

Name

Description

7:5

Reserved.

LOOPBACK

Loop Back. Set by user to enable loop

back mode. In loop back mode, the

SOUT is forced high. The modem signals

are also directly connected to the status

inputs (RTS to CTS, DTR to DSR, OUT1 to

RI, and OUT2 to DCD). Cleared by user to

be in normal mode.

PEN

Parity Enable Bit. Set by user to transmit

and check the parity bit. Cleared by user

for no parity transmission or checking.

STOP

Stop Bit. Set by user to transmit 1.5 stop

bits if the word length is 5 bits or 2 stop

bits if the word length is 6 bits, 7 bits, or

8 bits. The receiver checks the first stop

bit only, regardless of the number of

stop bits selected. Cleared by user to

generate 1 stop bit in the transmitted

data.

RTS

Request To Send. Set by user to force the

RTS output to 0. Cleared by user to force

the RTS output to 1.

DTR

Data Terminal Ready. Set by user to force

the DTR output to 0. Cleared by user to

force the DTR output to 1.

COMSTA0 Register

Name

Address

Default Value

Access

COMSTA0

0xFFFF0714

0x60

COMSTA0 is the line status register.

Table 52. COMSTA0 MMR Bit Descriptions

Bit

Name

Description

Reserved.

TEMT

COMTX Empty Status Bit. Set automatically if

COMTX is empty. Cleared automatically when

writing to COMTX.

THRE

COMTX and COMRX Empty. Set automatically if

COMTX and COMRX are empty. Cleared automati-

cally when one of the register receives data.

Break Error. Set when SIN is held low for more than

the maximum word length. Cleared automatically.

Framing Error. Set when invalid stop bit. Cleared

automatically.

Parity Error. Set when a parity error occurs.

Cleared automatically.

Overrun Error. Set automatically if data is over-

written before being read. Cleared automatically.

Data Ready. Set automatically when COMRX is

full. Cleared by reading COMRX.

COMSTA1 Register

Name

Address

Default Value

Access

COMSTA1

0xFFFF0718

0x00

COMSTA1 is a modem status register.

Table 53. COMSTA1 MMR Bit Descriptions

Bit

Name

Description

DCD

Data Carrier Eetect.

Ring Indicator.

DSR

Data Set Ready.

CTS

Clear To Send.

DDCD

Delta DCD. Set automatically if DCD changed

state since COMSTA1 last read. Cleared automati-

cally by reading COMSTA1.

TERI

Trailing Edge RI. Set if NRI changed from 0 to 1

since COMSTA1 last read. Cleared automatically

by reading COMSTA1.

DDSR

Delta DSR. Set automatically if DSR changed state

since COMSTA1 last read. Cleared automatically

by reading COMSTA1.

DCTS

Delta CTS. Set automatically if CTS changed state

since COMSTA1 last read. Cleared automatically

by reading COMSTA1.

COMSCR Register

Name

Address

Default Value

Access

COMSCR

0xFFFF071C

0x00

R/W

COMSCR is an 8-bit scratch register used for temporary

storage. It is also used in network addressable UART mode.

COMDIV2 Register

Name

Address

Default Value

Access

COMDIV2

0xFFFF072C

0x0000

R/W

COMDIV2 is a 16-bit fractional baud divide register.

Table 54. COMDIV2 MMR Bit Descriptions

Bit

Name

Description

FBEN

Fractional Baud Rate Generator Enable Bit.

Set by user to enable the fractional baud

rate generator. Cleared by user to generate

baud rate using the standard 450 UART

baud rate generator.

14:13

Reserved.

12:11

FBM[1-0]

M if FBM = 0, M = 4.

10:0

FBN[10-0]

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