Added memory map for vending machine

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+From [email protected] Fri Sep 14 20:28:08 2001
+Date: Sat, 8 Sep 2001 12:22:39 +0800
+From: Simon Fryer <[email protected]>
+To: Mark Tearle <[email protected]>
+Subject: [Vending Machine Memory Map]
+
+----- Forwarded message from Simon Fryer <[email protected]> -----
+
+Evening
+
+Had a look at the circuit diagram for the vending machine this evening. Tried
+to work out how all the I/O is arranged in memory as viewed by the HC11. For
+the most part, only the address lines A11, A12 and A13 are decoded into 
+useful addresses. This means that to drive all the devices except for the
+EPROM and the FLASH memory, A0 to A10 can be ignored and any value can be used. 
+The two memory chips actually care about the state of A0 to A10. I suspect that
+the devices built onto the HC11 sit in memory somewhere but I am not sure 
+where yet. 
+
+As far as I can tell, the memory map is as follows:
+0x8000 to 0xFFFF - EPROM. 27C256
+0x3800 to 0x3FFF - U14. 74HC374 - 8 * D type flip flops. Here the data bits
+       are latched and taken off to various devices. (read serial I/O by 
+       toggling data lines). 
+       D0, D1 - Bill Valadator
+       D2, D3 - Display - D2 is data, D3 is clock (I think)
+       D4, D5, D6 - Snack Motors. D4 is data for the row decoder. D5, D6
+               form part of the column decoders as far as I can tell. 
+0x3000 to 0x37FF - U13. 74HC374. For the changer - dispenses change and/or
+               counts change I think. Just latches data to the device. 
+0x0800 to 0x0FFF - U12. 40Z12. The Flash memory. 
+0x1800 to 0x1FFF - U7. 74HC245. This IC is a tristate buffer. It is used
+       for reading in the status of serveral switches. These switches are 
+       the cost, door and soldout switches. 
+0x2000 to 0c27FF - U5. 74HC245. This reads in the status of the switch 
+       block 1. These switces are LANG, LANG, FORCE, PROMO, MULTI and WN-SNK. 
+       suspect these are read on startup to provide running state. 
+0x2800 to 2FFF - U6, 74HC245. This reads row 1-5,6-9 onto the data bus. 
+
+There are some other bits of the circuit diagram that I want to get my head 
+around but I am going to leave that for another night. 
+
+Some more good news. I has having a look through one of the junk rooms at 
+home and found that I have a nice collection of 27C256 EPROMS sitting on some 
+old ISA boards. They have a difficult to remove plastic sticker over the UV
+window. These stickers are not Leatherman proof though. 
+
+Next couple of steps... read up on the internals of the HC11. We have the 
+simple model with only minimal useful stuff on board. 
+
+Also, to get a HC11 assembler and a working EPROM writer. 
+
+See Ya
+Simon
+
+-- 
+------------------------------------------------------------------------
+"Well, an engineer is not concerned with the truth; that is left to 
+philosophers and theologians: the prime concern of an engineer is 
+the utility of the final product."  
+Lectures on the Electrical Properties of Materials, L.Solymar, D.Walsh
+
+
+----- End forwarded message -----