User Manual

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)