====== Changes from R01 to R02 ======

New is in R0.2 the DIP-Switch S2. With the help of S2 we can use the KONTRON-conform Reset-Signal /PWRCLR (ECB C26) as RESET for PIO or like N8VEM the Signal /RESET (ECB C31)

====== Changes from R02 to R03: ======

- replacement from DIP-switches to jumper

- A0 to B/~A

- A1 to C/~D

- optimization of the look-ahead-carry logic

====== Differences between the ECB-4PIO and the jk82-PIO-WRAP ======

Between the two PCB are differences, not logically, but in design.

====== PIO Z80A ======

There layout of ECB-4PIO requires a rearrangement of IC8 - IC10 or PIO-0 - PIO-3 (jk82-PIO-WRAP) to IC8 to PIO, 11, 9, 12 and PIO-0 to PIO-3:

Jk82-PIO-WRAP ECB-4PIO

IC8 PIO-0 IC8 PIO-0

IC9 PIO-1 IC11 PIO-2

IC10 PIO-2 IC9 PIO-1

IC11 PIO-3 IC12 PIO-3

The order in the daisy chain is amended IC numbers are not influenced by there arrangement.

====== LS-TTL IC ======

By the replacement of some component types and the use of a new IC with open collector (IC10), Component numbering was reassigned:

Jk82-PIO-WRAP ECB-4PIO

IC1 74LS85 IC5 74LS85

IC2 74LS139 IC7 74LS139

IC3 74LS21 IC10 74LS21

IC4 74LS08 IC2 74LS08

IC5 74LS27 IC3 74LS27

IC6 74LS243 IC4 74LS541

IC7 74LS245 IC6 74LS245, 74LS645

IC1 74LS07

This was necessary because the driver IC6 (74LS243) of the circuit of jk82-PIO-WRAP by IC4 (74LS541) has been replaced. So now the AB2, AB3, IEI (by bus) and Ф(by bus) driven, as these signals are shared.

Furthermore, all /INT-outputs of PIO-0 PIO-3 are coupled via a resistor to +5 V (due to open-drain) and a driver of IC1 (74LS07) decouples the PIO from the ECB (Now are all PIO undriven with any signal on the ECB bus).

The DIL switch for the bridge /BAI to /BAO of jk82-PIO-WRAP is on the ECB-4PIO replaced by a fixed bridge.

The rest of the circuit was not changed. Es There is simply no longer WRAP box.

====== Resources ======

[[https://retrobrewcomputers.org/n8vem-pbwiki-archive/0/35845334/48860720/34743691/index.htm|Legacy site]]

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