3

MC2 Chip

ROM0 Refer to the table on the Local Bus Memory Map, Note 1, in Chapter 1.

Flash Access Time Control Register

The MVME172 is populated with a 120ns Flash memory device. Due to the wide range of Flash speeds, the contents can be changed by software to adjust for a specific speed.

ADR/SIZ

 

 

 

$FFF42040

(8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

15

14

13

 

12

 

11

 

10

9

8

 

 

 

 

 

 

 

 

 

 

 

NAME

 

 

 

 

 

FWEN

 

FT2

FT1

FT0

 

 

 

 

 

 

 

 

 

 

 

 

OPER

R

R

R

 

R

 

R/W

 

R/W

R/W

R/W

 

 

 

 

 

 

 

 

 

 

 

 

RESET

0

0

0

 

0

 

0

 

1 PL

1 PL

1 PL

 

 

 

 

 

 

 

 

 

 

 

 

FWEN Flash write enable function is internal to the ASIC for the MC2 chip. FWEN set to a 1 enables writes to the Flash memory space. FWEN set to a 0 inhibits writes to the Flash memory but the cycle completes without exception.

FT2-FT0Flash memory access time is controlled by the state of FT2-FT0. The following table defines the FT2-FT0 encoding (for the MVE172, whose bus frequency is 1/2 the processor frequency, only the 33MHz column applies).

FT2-

Flash Access <= N

Flash Access <= N

FT0

at 25 MHz where N =

at 33 MHz where N =

 

 

 

$0

60 ns

40 ns

 

 

 

$1

100 ns

70 ns

 

 

 

$2

140 ns

100 ns

 

 

 

$3

180 ns

130 ns

 

 

 

$4

220 ns

160 ns

 

 

 

$5

260 ns

190 ns

 

 

 

$6

300 ns

210 ns

 

 

 

$7

340 ns

240 ns

 

 

 

3-40

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Page 228
Image 228
Motorola MVME172 manual Flash Access Time Control Register, FT2 Flash Access = N