C251: WAIT STATE B ( WSB ) VS EXTENDED DATA FLOAT ( EDF )
Information in this article applies to:
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?
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.
Last Reviewed: Tuesday, March 27, 2007
of your data.