Usart receiver holding register, Usart transmitter holding register – Rainbow Electronics AT75C220 User Manual
Page 91
AT75C220
91
•
TXEMPTY: Transmitter Empty
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.
•
DMSI: Delta Modem Status Indication Interrupt
0 = No effect.
1 = There has been a change in the modem status delta bits since the last reset status bits command.
USART Receiver Holding Register
Name:
US_RHR
Access Type:Read-only
Reset Value: 0x0
•
RXCHR: Received Character
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.
USART Transmitter Holding Register
Name:
US_THR
Access Type:Write-only
Reset Value: Undefined
•
TXCHR: Character to be Transmitted
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
30
29
28
27
26
25
24
–
–
–
–
–
–
–
–
23
22
21
20
19
18
17
16
–
–
–
–
–
–
–
–
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
RXCHR
7
6
5
4
3
2
1
0
RXCHR
31
30
29
28
27
26
25
24
–
–
–
–
–
–
–
–
23
22
21
20
19
18
17
16
–
–
–
–
–
–
–
–
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
TXCHR
7
6
5
4
3
2
1
0
TXCHR