With the PCB's in and the initial hardware check finished and me delaying far too long on getting back to this project, it was time to move on to verifying that my intended hardware functionality did, in fact, work as planned. There are several functional blocks that need to be tested, both on the AVR … Continue reading Hardware test – 2nd phase
I decided to add-on the 82C51A just to try some Z80 coding. I figured that I already had the 82C51A UART and its smaller in size (DIP-28) than an 82C55 PIO (DIP-40). I added it to the solder-less bread board and checked all my connections for (proper) continuity. All tested well for continuity, so off … Continue reading Z80 testing – Simple program to exercise the UART
In the previous post, I stated that I was finally able to get the Z88DK software development suite up and running. I should point out that I am running Linux Mint 13 on an AMD64 CPU. DISTRIB_ID=LinuxMint DISTRIB_RELEASE=13 DISTRIB_CODENAME=maya DISTRIB_DESCRIPTION="Linux Mint 13 Maya" NAME="Ubuntu" VERSION="12.04.5 LTS, Precise Pangolin" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu precise (12.04.5 LTS)" VERSION_ID="12.04" … Continue reading Getting the Z88DK software development suite up and running
I have been testing the current breadboard circuit. I decided to add in an 82C51A UART with the intention of writing some code just to test the Z88DK software development suite, which I finally got to compile properly. More on that in another post. As stated in the last post, I had a few I/O pins … Continue reading More testing of the memory and I/O address decoder PLD
It was previously decided that the AVR could not respond fast enough to a DISK or UART chip select signal by asserting the Z-80's WAIT line while the AVR serviced the Z80's I/O request. Thus, a wait-state generator was needed. More precisely, a programmable wait-state generator, so the design criteria was to create a programmable wait-state … Continue reading Moving the programmable wait-state generator into a GAL22V10
The plan is to use the AT90USB1286 (PJRC TEENSY 2.0 ++ board) as a virtual UART and "Disk Drive" (using an SD memory card). Testing the AVR's response time to DISK and UART selects as interrupts on the INT0 input is a problem. Using INT0, it takes 14 clock cycles to respond and set the … Continue reading 1st attempt at a programmable wait-state generator
It would be nice if I could reduce parts count by emulating the 82C51A UART (or MC6850) using the AT90USB1286. Since the INT[7..0] interrupt pins are selectable between level or +/- edge sensitive and the pin-change interrupts will respond to ANY change of state, I will stick with the INT[7..0] pins. I want to trigger … Continue reading Testing the AVR’s interrupt latency.