Rainbow Electronics AT75C220 - 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)