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January 19, 2000 SX18AC/SX20AC/SX28AC/SX18AC75/SX20AC75/SX28AC75 Configurable Communications Controllers with EE/Flash Program
Memory, In-System Programming Capability and On-Chip Debug
1.0 PRODUCT OVERVIEW 1.1    Introduction The  Scenix  SX  family  of  configurable  communications
controllers are fabricated in an advanced CMOS process
technology.   The   advanced   process,   combined   with   a
RISC-based  architecture,  allows  high-speed  computa-
tion, flexible I/O control, and efficient data manipulation.
Throughput  is enhanced by  operating  the device  at  fre-
quencies up to 50/75 MHz and by optimizing the instruc-
tion  set  to  include  mostly  single-cycle  instructions.  In
addition,  the  SX  architecture  is  deterministic  and  totally
reprogramable. The unique combination of these charac-
teristics  enables the device to implement hard real-time
functions  as  software  modules  (Virtual  Peripheral™)  to
replace traditional hardware functions.
On-chip  functions  include  a  general-purpose  8-bit  timer
with prescaler, an analog comparator, a brown-out detec-
tor,  a  watchdog  timer,  a  power-save  mode  with  multi-
source wakeup capability, an internal R/C oscillator, user-
selectable clock modes, and high-current outputs.
Figure 1-1. Block Diagram Interrupt MIW U Port B Comp Power-O n Reset RESET 8-bit W atchdog Tim er (W DT) 8-bit Tim er RTCC 8 8 8 Port C 8 8 Port A 8 4 Internal Data Bus  In-System
Debugging
   In-System
Programm ing
2k W ords
EEPRO M
System Clock Brown-O ut MIW U M CLR  O SC
Driver
4M Hz
 Internal
RC  OSC
 Clock
Select
4 or 1 136 Bytes SRAM Address W rite Data Read Data Instruction W FSR STATUS PC M O DE OPTIO N System  Clock OSC1   O SC2 Fetch 8 8 12 Address 12 8 8 8 8 ALU 8 8 8 3 RTCC Analog 8 Interrupt Stack    PC 
3 Level
Decode Executive W rite Back IREAD Stack Instruction Pipeline Prescaler for RTCC                 or
Prescaler for W DT