8XC196MC, MD, MH USER’S MANUAL

CCR0 (Continued)

no direct access†

The chip configuration 0 (CCR0) register controls powerdown mode, bus-control signals, and internal memory protection. Three of its bits combine with two bits of CCR1 to control wait states and bus width.

7

LOC1

LOC0

IRC1

IRC0

 

 

 

 

0

ALE

WR

BW0

PD

 

 

 

 

Bit

Bit

 

 

 

Function

Number

Mnemonic

 

 

 

 

 

 

 

 

 

 

3

ALE

Address Valid Strobe and Write Strobe

 

 

These bits define which bus-control signals will be generated during

2

WR

 

 

external read and write cycles.

 

 

ALE

WR

 

 

 

0

 

0

address valid with write strobe mode

 

 

 

 

 

(ADV#, RD#, WRL#, WRH#)

 

 

0

 

1

address valid strobe mode

 

 

 

 

 

(ADV#, RD#, WR#, BHE#)

 

 

1

 

0

write strobe mode

 

 

 

 

 

(ALE, RD#, WRL#, WRH#)

 

 

1

 

1

standard bus-control mode

 

 

 

 

 

(ALE, RD#, WR#, BHE#)

 

 

 

1

BW0

Buswidth Control

 

 

This bit, along with the BW1 bit (CCR1.2), selects the bus width.

 

 

BW1

BW0

 

 

 

0

 

0

illegal

 

 

0

 

1

16-bit only

 

 

1

 

0

8-bit only

 

 

1

 

1

BUSWIDTH pin controlled

 

 

 

0

PD

Powerdown Enable

 

 

Controls whether the IDLPD #2 instruction causes the microcontroller to

 

 

enter powerdown mode. If your design uses powerdown mode, set this

 

 

bit when you program the CCBs. If it does not, clearing this bit when you

 

 

program the CCBs will prevent accidental entry into powerdown mode.

 

 

0

= disable powerdown mode

 

 

1

= enable powerdown mode

 

 

 

 

 

 

The CCRs are loaded with the contents of the chip configuration bytes (CCBs) after reset, unless the microcontroller is entering programming modes (see “Entering Programming Modes” on page 16-13), in which case the programming chip configuration bytes (PCCBs) are used. The CCBs reside in nonvolatile memory at addresses 2018H (CCB0) and 201AH (CCB1).

Figure 15-1. Chip Configuration 0 (CCR0) Register (Continued)

15-8

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Intel 8XC196MC, 8XC196MD, 8XC196MH manual CCR0, Ale, BW1 BW0