2 Date: Sat, 8 Sep 2001 12:22:39 +0800
5 Subject: [Vending Machine Memory Map]
11 Had a look at the circuit diagram for the vending machine this evening. Tried
12 to work out how all the I/O is arranged in memory as viewed by the HC11. For
13 the most part, only the address lines A11, A12 and A13 are decoded into
14 useful addresses. This means that to drive all the devices except for the
15 EPROM and the FLASH memory, A0 to A10 can be ignored and any value can be used.
16 The two memory chips actually care about the state of A0 to A10. I suspect that
17 the devices built onto the HC11 sit in memory somewhere but I am not sure
20 As far as I can tell, the memory map is as follows:
21 0x8000 to 0xFFFF - EPROM. 27C256
22 0x3800 to 0x3FFF - U14. 74HC374 - 8 * D type flip flops. Here the data bits
23 are latched and taken off to various devices. (read serial I/O by
25 D0, D1 - Bill Valadator
26 D2, D3 - Display - D2 is data, D3 is clock (I think)
27 D4, D5, D6 - Snack Motors. D4 is data for the row decoder. D5, D6
28 form part of the column decoders as far as I can tell.
29 0x3000 to 0x37FF - U13. 74HC374. For the changer - dispenses change and/or
30 counts change I think. Just latches data to the device.
31 0x0800 to 0x0FFF - U12. 40Z12. The Flash memory.
32 0x1800 to 0x1FFF - U7. 74HC245. This IC is a tristate buffer. It is used
33 for reading in the status of serveral switches. These switches are
34 the cost, door and soldout switches.
35 0x2000 to 0c27FF - U5. 74HC245. This reads in the status of the switch
36 block 1. These switces are LANG, LANG, FORCE, PROMO, MULTI and WN-SNK.
37 suspect these are read on startup to provide running state.
38 0x2800 to 2FFF - U6, 74HC245. This reads row 1-5,6-9 onto the data bus.
40 There are some other bits of the circuit diagram that I want to get my head
41 around but I am going to leave that for another night.
43 Some more good news. I has having a look through one of the junk rooms at
44 home and found that I have a nice collection of 27C256 EPROMS sitting on some
45 old ISA boards. They have a difficult to remove plastic sticker over the UV
46 window. These stickers are not Leatherman proof though.
48 Next couple of steps... read up on the internals of the HC11. We have the
49 simple model with only minimal useful stuff on board.
51 Also, to get a HC11 assembler and a working EPROM writer.
57 ------------------------------------------------------------------------
58 "Well, an engineer is not concerned with the truth; that is left to
59 philosophers and theologians: the prime concern of an engineer is
60 the utility of the final product."
61 Lectures on the Electrical Properties of Materials, L.Solymar, D.Walsh
64 ----- End forwarded message -----