Hi!
I wonder how you would bulid a SD-memory interface for for instance a Motorola 6809 CPU.
I have built a very primitive and similar CPU using a Xilinx CPLD (XCR3512XL).
I have, after hard work, managed to make three instructions work (JMP, LDA and STA).
There are two problems though:
1) The micro-programming of the instructions are hard and requires tedious EPROM-reprogramming as I go.
2) Speed is slow (<4MHz) due to old EPROMs (CPLD-limit is however some 150MHz)
I would very much want to upgrade this design now that my concept work.
One thought is to migrate the design to a FPGA (with internal ROM-functions) instead.
It however seems like I have to reprogram the whole CPU in that case.
So I'm thinking that maybe I could use a SD-memory as both "Hard Drive"/Program memory and "Instruction Register" instead (two separate SDs are however needed).
Please direct me to a site that in detail explains how a SD-memory work HW-wise. I have searched the web but found almost nothing of the kind.
Best regards, Roger
PS
Attaching a picture of my current CPLD-version.
I wonder how you would bulid a SD-memory interface for for instance a Motorola 6809 CPU.
I have built a very primitive and similar CPU using a Xilinx CPLD (XCR3512XL).
I have, after hard work, managed to make three instructions work (JMP, LDA and STA).
There are two problems though:
1) The micro-programming of the instructions are hard and requires tedious EPROM-reprogramming as I go.
2) Speed is slow (<4MHz) due to old EPROMs (CPLD-limit is however some 150MHz)
I would very much want to upgrade this design now that my concept work.
One thought is to migrate the design to a FPGA (with internal ROM-functions) instead.
It however seems like I have to reprogram the whole CPU in that case.
So I'm thinking that maybe I could use a SD-memory as both "Hard Drive"/Program memory and "Instruction Register" instead (two separate SDs are however needed).
Please direct me to a site that in detail explains how a SD-memory work HW-wise. I have searched the web but found almost nothing of the kind.
Best regards, Roger
PS
Attaching a picture of my current CPLD-version.
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