User Manual

AT75C220

• 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

76543210

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

76543210

TXCHR