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8XC251SA, SB, SP, SQ USER'S MANUAL
12.2.2
Power Off Flag ........................................................................................................12-1
12.3
IDLE MODE ................................................................................................................. 12-4
12.3.1
Entering Idle Mode ..................................................................................................12-4
12.3.2
Exiting Idle Mode ....................................................................................................12-5
12.4
POWERDOWN MODE ................................................................................................ 12-5
12.4.1
Entering Powerdown Mode .....................................................................................12-6
12.4.2
Exiting Powerdown Mode .......................................................................................12-6
12.5
ON-CIRCUIT EMULATION (ONCE) MODE ................................................................ 12-7
12.5.1
Entering ONCE Mode .............................................................................................12-7
12.5.2
Exiting ONCE Mode ................................................................................................12-7
CHAPTER 13
13.1
OVERVIEW ................................................................................................................. 13-1
13.2
EXTERNAL BUS CYCLES .......................................................................................... 13-3
13.2.1
Bus Cycle Definitions ..............................................................................................13-3
13.2.2
Nonpage Mode Bus Cycles ....................................................................................13-4
13.2.3
Page Mode Bus Cycles ...........................................................................................13-5
13.3
WAIT STATES ............................................................................................................. 13-8
13.4
EXTERNAL BUS CYCLES WITH CONFIGURABLE WAIT STATES.......................... 13-8
13.4.1
Extending RD#/WR#/PSEN# ..................................................................................13-8
13.4.2
Extending ALE ......................................................................................................13-10
13.5
EXTERNAL BUS CYCLES WITH REAL-TIME WAIT STATES................................. 13-10
13.5.1
Real-time WAIT# Enable (RTWE) .........................................................................13-12
13.5.2
Real-time WAIT CLOCK Enable (RTWCE) ...........................................................13-12
13.5.3
Real-time Wait State Bus Cycle Diagrams ............................................................13-12
13.6
CONFIGURATION BYTE BUS CYCLES................................................................... 13-15
13.7
PORT 0 AND PORT 2 STATUS ................................................................................ 13-16
13.7.1
Port 0 and Port 2 Pin Status in Nonpage Mode ....................................................13-16
13.7.2
Port 0 and Port 2 Pin Status in Page Mode ..........................................................13-17
13.8
EXTERNAL MEMORY DESIGN EXAMPLES............................................................ 13-18
13.8.1
Example 1: RD1:0 = 00, 18-bit Bus, External Flash and RAM ..............................13-18
13.8.2
Example 2: RD1:0 = 01, 17-bit Bus, External Flash and RAM ..............................13-20
13.8.3
Example 3: RD1:0 = 01, 17-bit Bus, External RAM ..............................................13-22
13.8.4
Example 4: RD1:0 = 10, 16-bit Bus, External RAM ..............................................13-24
13.8.5
Example 5: RD1:0 = 11, 16-bit Bus, External EPROM and RAM .........................13-26
13.8.5.1
An Application Requiring Fast Access to the Stack .........................................13-26
13.8.5.2
An Application Requiring Fast Access to Data .................................................13-26
13.8.6
Example 6: RD1:0 = 11, 16-bit Bus, External EPROM and RAM .........................13-29
13.8.7
Example 7: RD1:0 = 01, 17-bit Bus, External Flash ..............................................13-30
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