XR88C681_06 Datasheet, PDF (2/101 Pages) Exar Corporation – CMOS Dual Channel UART (DUART)

XR88C681
TXDA RXDA
TXDB RXDB
IP0 - IP6
OP0 - OP7
TSR
RSR
THR
RHR
Mode Registers
Status Register
Channel A
TSR
RSR
THR
RHR
Mode Registers
Status Register
Channel B
IPR
Change of
State Detectors
IPCR
ACR
Input Port
OPR
Output Port
Function Select
Logic
OPCR
Output Port
Internal Data Bus
Data
Bus
Buffer
Operation Control
CRA CRB
Command Decoder
Address Decoder
Interrupt Control
IVR
MISR
IMR
ISR
CSRA
Timing
CSRB
Bit Rate
Generator
Counter/Timer
Oscillator
D0 - D7 A0 - A3 -RD -WR -CS RESET IEI IEO -IACK -INTR
X1/CLK X2
Figure 1. Block Diagram of the XR88C681
Rev. 2.11
2