5

MCECC

RB3 Read Bit 3 is a read only bit that is always 0.

Difference from MEMC040: bit = WPB (write-per-bit input strap status) for MEMC040; bit = 0 for MCECC (WPB = 0 on current versions of MVME172).

RB4 Read Bit 4 is a read only bit that is always 1.

Difference from MEMC040: bit = EXTPEN (external parity enable input strap status) for MEMC040; bit = 1 for MCECC (EXTPEN = 1 on current versions of MVME172).

FSTRD FSTRD reflects the state of the FSTRD bit in the Defaults Register 1. When 1, this bit indicates that DRAM reads are operating at full speed. When 0, it indicates that DRAM read accesses are slowed by one clock cycle to accommodate slower DRAM devices.

Difference from MEMC040: NONE except that it is an input pin on the MEMC040; while it is a register bit that is initialized by the reset serial bit stream on the MCECC.

Dummy Register 0

Dummy Register 0 is hard-wired to all zeros. Writes to this register are ignored; however, the MCECC always terminates the cycles properly with TA*.

Difference from MEMC040: register = Alternate Status for MEMC040; register = $00 for MCECC.

ADR/SIZ

 

 

1st $FFF4300C/2nd $FFF4310C (8-bits)

 

 

 

 

 

 

 

 

 

 

 

BIT

31

30

 

29

28

27

26

25

24

 

 

 

 

 

 

 

 

 

 

NAME

0

0

 

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

OPER

R

R

 

R

R

R

R

R

R

 

 

 

 

 

 

 

 

 

 

RESET

X

X

 

X

X

X

X

X

X

 

 

 

 

 

 

 

 

 

 

5-16

Computer Group Literature Center Web Site

Page 306
Image 306
Motorola MVME172 manual Dummy Register, RB3 Read Bit 3 is a read only bit that is always