Comments (5)
Thanks!
Bit 3 needs a bit more investigation, because this may depend on a pull-up / pull-down present in the datasette. Concerning bit 6 and 7 (and probably also bit 3 without datasette), the value read may depend on the value that was on the (virtual) pin before the direction was set to input. For instance:
lda #$ff
sta 0
sta 1
lda #0
sta 0
[delay]
lda 1 might actually have bits 6 and 7 set. depending on [delay]
It is known that the bits fall off to 0, but I'll have to see how long that takes on my C64.
from 1541ultimate.
According to the service manual of the 1530/1531 datasette, there are VARIOUS circuits used. There is ONE model that has a pull-up on the write pin; all others don't. So I think it is safe to assume that in most cases there is no pull-up on the write line (bit 3), so it should behave similar to bit 6 and 7. On the other hand, one could reason that the leakage current of the 7414 will likely have a preference for a logic '1', so maybe assuming a pull-up on bit 3 is not wrong.
from 1541ultimate.
With a little test program on my C64, bit 6 and 7 fall back to zero after approx 48000-49000 cycles, thus approx 49..50 ms. In case of my C64, bit 7 falls off a bit earlier than bit 6, but the difference is roughly 6000 cycles max. Interestingly, bit 3 remains 1! .... for... sit back.... 5 SECONDS. This is without datasette attached.
from 1541ultimate.
Ok.. found it.. On my board revision (Assy 250425), there is 470 pF connected to P3... Hence the 5 second delay. Let's say the bit flips from 1 to 0 at roughly 1V, this means that the voltage had dropped 4V in 5 seconds. This means that the leakage current is in the order of magnitude of I = (c * v) / t = 0.38 nA. That is really impressively small for NMOS. Other approach: what is the capacitance of the internal non-connected I/O pad of the 6510? Linear extrapolation: 470 pF => 5 seconds, 50 ms = 0.01 * 470 pF = 4.7pF. Yeah, sounds about right.
from 1541ultimate.
Fixed in 1.1A.
from 1541ultimate.
Related Issues (20)
- Ultimate II+L issues 3.11 (11e) HOT 3
- U2+L - I was testing out Drive and Kernel ROMs but now just get blank screens and unable to access any menu HOT 12
- Ultimate64 3.11: GeoRAM disabled at Reset+Run & Reset+Load
- [UII - FW3.11 - HTTP API - LIMITATION] PUT /v1/runners:sidplay 74 char limit
- [UII - FW3.11 - HTTP API - BEHAVIOUR] Floppy Drives - GET /v1/drives response behaviour
- [UII - FW3.11 - HTTP API - BEHAVIOUR] Printer Emulation - GET /v1/drives
- [UII - FW3.11 - HTTP API - MISSINGENDPOINT] /v1/configs/C64 and Cartridge Settings/UltiDOS: Allow SetDate
- [UII - FW3.11 - HTTP API - MISSINGFUNC] Set/Load Alternate Kernal missing
- [HTTP API - FEATUREREQ] /v1/version to return more info.
- [HTTP API - FEATUREREQ] Implement Server Sent Events (SSEs)
- [HTTP API - FEATUREREQ] Allow GET /v1/files/<path>:info to return extended information regarding to file type (extension).
- [UII - FW3.11 - BASIC TOKENIZER - BUG] Basic tokenizer in fw3.11 has a bug
- [HTTP API - FEATUREREQ] API end-point to retrieve list of files on the given location
- Error compiling... HOT 6
- [HTTP API - FEATUREREQ] Retrieve a on device file by providing its full path
- [HTTP API - FEATUREREQ] API End-point to save arbitrary file to provided path
- Feature proposal: telnet support for use with Swiftlink implementation
- U64 [1.43] [3.11] When using poweroff REST method machine turns off with a very loud POP in volume
- Ultimate 64 crash using ExFAT HOT 2
- [U2+L WiFi Module - FEATUREREQ] Bluetooth Audio Output
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from 1541ultimate.