at75c220 ATMEL Corporation, at75c220 Datasheet - Page 91

• Manufacturer Part Number: at75c220
• Description: Smart Internet Appliance Processor Siap
• Manufacturer: ATMEL Corporation

•
•
USART Receiver Holding Register
Name:
Access Type:Read-only
Reset Value: 0x0
•
USART Transmitter Holding Register
Name:
Access Type:Write-only
Reset Value: Undefined
•
TXEMPTY: Transmitter Empty
DMSI: Delta Modem Status Indication Interrupt
RXCHR: Received Character
TXCHR: Character to be Transmitted
0 = There are characters in either US_THR or the Transmit Shift Register or a break is being transmitted.
1 = There are no characters in US_THR and the Transmit Shift Register and break is not active.
Equal to zero when the USART is disabled or at reset. Transmitter enable command (in US_CR) sets this bit to one.
0 = No effect.
1 = There has been a change in the modem status delta bits since the last reset status bits command.
Last character received if RXRDY is set. When number of data bits is less than eight, the bits are right-aligned.
All unused bits read as zero.
Next character to be transmitted after the current character if TXRDY is not set. When number of data bits is less than
eight, the bits are right-aligned.
31
23
15
31
23
15
–
–
–
7
–
–
–
7
US_RHR
US_THR
30
22
14
30
22
14
–
–
–
6
–
–
–
6
29
21
13
29
21
13
–
–
–
5
–
–
–
5
28
20
12
28
20
12
–
–
–
4
–
–
–
4
RXCHR
TXCHR
27
19
11
27
19
11
–
–
–
3
–
–
–
3
26
18
10
26
18
10
–
–
–
2
–
–
–
2
25
17
25
17
–
–
9
–
1
–
–
9
–
1
RXCHR
TXCHR
24
16
24
16
–
–
8
0
–
–
8
0
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