Cache Programming Model

Table 4-7. External Fetch Size Based on Miss Address and CLNF

CLNF[1:0]

 

Longword Address Bits

 

 

 

 

 

00

01

10

11

 

 

 

 

 

 

00

Line

Line

Line

Longword

 

 

 

 

 

01

Line

Line

Longword

Longword

 

 

 

 

 

10

Line

Line

Line

Line

 

 

 

 

 

11

Line

Line

Line

Line

 

 

 

 

 

4.4.2.2Access Control Registers (ACR0, ACR1)

The ACRs provide a definition of memory reference attributes for two memory regions (one per ACR). This set of effective attributes is defined for every memory reference using the ACRs or the set of default attributes contained in the CACR. The ACRs are examined for every processor memory reference that is not mapped to the Flash or SRAM memories.

The ACRs are 32-bit write-only supervisor control register. They are accessed in the CPU address space via the MOVEC instruction with an Rc encoding of 0x004 and 0x005. The ACRs can be read when in background debug mode (BDM). At system reset, both registers are cleared.

31

24

23

16

Field

Reset

R/W

 

 

 

AB

 

 

 

 

AM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0000_0000_0000_0000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15

14

13

12

7

6

5

4

3

2

1

0

Field

EN

 

SM

 

 

CM

BUFW

 

WP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset

 

 

 

 

 

0000_0000_0000_0000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R/W

 

 

 

 

 

 

W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4-3. Access Control Registers (ACR0, ACR1)

 

 

 

 

 

 

 

 

 

 

 

 

Table 4-8. ACR Field Descriptions

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bits

 

Name

 

 

 

Description

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

31–24

 

 

AB

 

Address base. This 8-bit field is compared to address bits [31:24] from the processor's local bus under

 

 

 

 

 

 

control of the ACR address mask. If the address matches, the attributes for the memory reference are

 

 

 

 

 

 

sourced from the given ACR.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

22–16

 

 

AM

 

Address mask. This 8-bit field can mask any bit of the AB field comparison. If a bit in the AM field is

 

 

 

 

 

 

set, then the corresponding bit of the address field comparison is ignored.

 

 

 

 

 

 

 

 

 

 

 

 

 

15

 

 

EN

 

Enable. The EN bit defines the ACR enable. Hardware reset clears this bit, disabling the ACR.

 

 

 

 

 

 

 

0

ACR disabled

 

 

 

 

 

 

 

 

 

 

 

 

 

1

ACR enabled

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MOTOROLA

Chapter 4. Cache

4-11

Page 135
Image 135
Motorola MCF5281, MCF5282 Access Control Registers ACR0, ACR1, External Fetch Size Based on Miss Address and Clnf, Bufw