General infos to the JIFFYDOS IEC bus routines:
b.i. = branches if
*xyz = diference between COMMODORE- and JIFFYDOS- KERNAL/DOS
lda $dd00 4 the number is the length of the order in microseconds (uS)
Because I have problems with "high/low" I use "active/inactive":
active inactive
logical high logical low
IEC-bus 0V 5V
1541 in&out high low
C64 outputs high low
C64 inputs low high
CBM saved money and didn't use input inverters at the C64.
The 1541 runs with 1 MHz
The (American) NTSC-C64 runs with 1.0227 MHz
The (European) PAL-C64 runs with 0.9852 MHz
HD HD
& no &
CBM JIFF S-JI JIFF JIFF FD para para RAM-
1541 1541 1541 1571 1581 2000 cabl cabl LINK
Load 202 Blocks: 127,2 13,2 8,7 9,1 8,3 7,7 6,2 2,3 1,2
Save 154 Blocks: 105,3 43,4 21,0 41,8 20,7 19,6 15,7 3,0 2,4
C64 CIA port of serial bus $dd00:
bit 7 DATA-IN (not inverted)
bit 6 CLOCK-IN (not inverted)
bit 5 DATA-OUT (inverted)
bit 4 CLOCK-OUT (inverted)
bit 3 ATTENTION-OUT ATN (inverted)
bit 2 pin M of userport
bit 1&0 VIC-bank
1541 VIA port of serial bus $1800:
bit 7 ATTENTION-IN (inverted)
bit 6&5 jumper for device-number 8-11
bit 4 ATTENTION-ACKNOWLEDGE ATNack (doesn't set the ATN-line of the serial
bus, but indirectly the data-line. If the logical status of the
ATN-line of the serial bus is opposite to the status of this bit,
then the 1541 sets (over an iverter chip) the data line to active.
The activated data-line is the signal for the C64 that the floppy
isn't ready and the C64 must wait.)
bit 3 CLOCK-OUT (inverted)
bit 2 CLOCK-IN (inverted)
bit 1 DATA-OUT (inverted)
bit 0 DATA-IN (inverted)
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2000/01/30
Near Letter Quantity
Jochen Adler
NLQ@gmx.de
http://home.t-online.de/home/dadler/
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