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WAIT STATE B ( WSB ) VS EXTENDED DATA FLOAT ( EDF )

Applies to: C251 C Compiler

Answer


Information in this article applies to:


QUESTION

Looking at the Intel 251SB User's Manual page #71, it shows that UCFG1, bit number 3, has a mnemonic called WSB, and bits 2:1 are called WSB1:0#.

Why did you choose EDF instead of WSB (for bit number 3) as a bit mnemonic inside the START251.ASM?

Here's the section of the start251.asm where I noticed this:

; Extended Data Float (EDF) Timing Feature
; EDF        Val  Description
 ; ----       ---  -----------
 EDF  EQU 0  ; 1 = Standard (Compatibility) Mode
 ;           ; 0 = extend data float timing for slow memory devices

Why is the mnemonic changed from WSB to EDF?

ANSWER

There were 3 steps of the 251: A-Step, B-Step, and C-Step. Only the C-Step devices are currently manufactured.

The WSB bit (UCFG1 bit 3) was used only on the A-STEP parts. It was not used on the B-STEP and C-STEP devices.

The EDF bit (UCFG1 bit 3) was introduced in the 251Tx devices. Refer to the User's Manual Addendum for more information on this bit.

MORE INFORMATION

Article last edited on: 2007-03-27 15:59:40

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