Programming Model

SRAM Space Size Register

ADR/SIZ

 

 

 

$FFF42024 (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

15

14

13

 

12

11

 

10

9

8

 

 

 

 

 

 

 

 

 

 

 

NAME

 

 

 

 

 

 

 

SEN

SZ1

SZ0

 

 

 

 

 

 

 

 

 

 

 

OPER

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

0 PL

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SEN SRAM ENABLE must be set to a one before the SRAM can be accessed.

SZ1-SZ0The size bits configure the SRAM decoder for a particular memory size. The following table defines their use. Note that the table specifies the allowed bit combinations for SZ1 - SZ0. Any other combinations generate unpredictable results.

SZ1 - SZ0 are set equal to the SZ1 - SZ0 bits of the DRAM/SRAM Options Register. SZ1 - SZ0 are programmable to facilitate diagnostic software.

Table 3-7. SRAM Size Control Bit Encoding

SZ1 - SZ0

Memory Size

 

 

$0

Reserved (do not use)

 

 

$1

512 KB (or 128 KB)

 

 

$2

1 MB

 

 

$3

2 MB

 

 

Note For an MVME172 with 128 KB of SRAM, the software must program SZ1-SZ0 = $1 (512 KB). Therefore, the SRAM contents will repeat in the memory map.

3

http://www.mcg.mot.com/literature

3-29

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Image 217
Motorola MVME172 manual Sram Space Size Register, SZ1 SZ0 Memory Size