Usart user interface – Rainbow Electronics AT75C220 User Manual
Page 82

AT75C220
82
USART User Interface
Base Address USART A: 0xFF018000
Base Address USART B: 0xFF01C000
Notes:
1. This is either 0x18 or 0x418 depending on the value of bootn and modem control inputs.
2. This depends on the value of modem control input signals, as these are reflected in this register.
Offset
Register Name
Description
Access
Reset Value
0x00
US_CR
Control Register
Write-only
–
0x04
US_MR
Mode Register
Read/write
0
0x08
US_IER
Interrupt Enable Register
Write-only
–
0x0C
US_IDR
Interrupt Disable Register
Write-only
–
0x10
US_IMR
Interrupt Mask Register
Read-only
0
0x14
US_CSR
Channel Status Register
Read-only
0x18
(1)
0x18
US_RHR
Receiver Holding Register
Read-only
0
0x1C
US_THR
Transmitter Holding Register
Write-only
–
0x20
US_BRGR
Baud Rate Generator Register
Read/write
0
0x24
US_RTOR
Receiver Time-out Register
Read/write
0
0x28
US_TTGR
Transmitter Time-guard Register
Read/write
0
0x2C
–
Reserved
–
–
0x30
US_RPR
Receive Pointer Register
Read/write
0
0x34
US_RCR
Receive Counter Register
Read/write
0
0x38
US_TPR
Transmit Pointer Register
Read/write
0
0x3C
US_TCR
Transmit Counter Register
Read/write
0
0x40
US_MC
Modem Control Register
Write-only
–
0x44
US_MS
Modem Status Register
Read-only
(See Note 2)