P112 README
===========
The P112 is notable because it was the first of the hobbyist single board
computers to reach the production stage. The P112 hobbyist computers
were relatively widespread and inspired other hobbyist centered home brew
computing projects such as N8VEM home brew computing project. The P112
project still maintains many devoted enthusiasts and has an online
repository of software and other information.
The P112 computer originated as a commercial product of "D-X Designs Pty
Ltd" of Australia. They describe the computer as "The P112 is a stand-alone
8-bit CPU board. Typically running CP/M (tm) or a similar operating system,
it provides a Z80182 (Z-80 upgrade) CPU with up to 1MB of memory, serial,
parallel and diskette IO, and realtime clock, in a 3.5-inch drive form factor.
Powered solely from 5V, it draws 150mA (nominal: not including disk drives)
with a 16MHz CPU clock. Clock speeds up to 24.576MHz are possible."
The P112 board was last available new in 1996 by Dave Brooks. In late 2004
on the Usenet Newsgroup comp.os.cpm, talk about making another run of P112
boards was discussed. David Griffith decided to produce additional P112 kits
with Dave Brooks blessing and the assistance of others. In addition Terry
Gulczynski makes additional P112 derivative hobbyist home brew computers.
Hal Bower was very active in the mid 1990's on the P112 project and ported
the "Banked/Portable BIOS".
Dave Brooks was successfully funded through Kickstarter for and another
run of P112 boards in November of 2012.
Pin Configuration
=================
The P112 is based on the 5V Z8018216FSG running at 16MHz. The Z8018216FSG
comes in a 100-pin QFP package:
PIN NAME
1 /INT0 INT0, pulled up, J1 DIN48 pin 13C
2 /INT1/PC6 FINTR, Floppy disk controller
3 /INT2/PC7 PINTR1, Floppy disk controller
4 ST ST, to AEN of Floppy disk controller
5 A0 A0-A12 Common memory bus
...
17 A12 " "
18 VSS ---
19 A13 A13-A17 Common memory bus
...
23 A17 " "
24 A18/TOUT A18 Common memory bus
25 VDD ---
26 A19 A19 Common memory bus
27 D0 D0-D4 Common memory bus
...
30 D3 " "
31 D4 D4-D7 Common memory bus
...
34 D7 " "
35 /RTS0/PB0 RTS0, 20-pin P14, pin 3
36 /CTS0/PB1 CTS0, pulled high (U16), 20-pin P14, pin 4
37 /DCD0/PB2 DCD0, pulled high (U16), 20-pin P14, pin 10
38 TXA0/PB3 TXA0, 20-pin P14, pin 8
39 RXA0/PB4 RXA0, pulled high (U17), 20-pin P14, pin 2
40 TXA1/PB5 TXA1, 20-pin P14, pin 1
41 RXA1/PB6 RXA1, pulled high (U17), 20-pin P14, pin 9
42 RXS//CTS1/PB7 CTS1, pulled high (U17), 20-pin P14, pin 7
43 CKA0//DREQ0 /DREQ0, DMA Request Select, 5-pin P2, pin 2
44 VSS ---
45 CKA1//TEND0 /TEND0, J1 DIN48 pin 14A
46 TXS//DTR//REQB//HINTR DTRB, 20-pin P14, pin 6
47 CKS//W//REQB//HTXRDY SIORQ, DMA Request Select, 5-pin P2, pin 5 (may be DREQ 0 or DREQ1)
48 /DREQ1 /DREQ1, DMA Request Select, 5-pin P2, pin 4
49 VDD ---
50 /TEND1//RTSB//HRXRDY NB /TEND1 = RTSB, 20-pin P14, pin 5; J1 DIN48 pin 14B
51 /RAMCS /RAMCS, Chip select logic (U11B); also J1 DIN48 pin 9B
52 /ROMCS /ROMCS, Chip select logic (P2); also J1 DIN48 pin 12B
53 EV1 Grounded
54 EV2 Grounded
55 PA0/HD0 IO, U6 DS1202 Serial Timekeeping chip
56 PA1/HD1 CLK, U6 DS1202 Serial Timekeeping chip
57 PA2/HD2 /RST, U6 DS1202 Serial Timekeeping chip
58 PA3/HD3 N/C
59 PA4/HD4 N/C
60 PA5/HD5 U12 NMF0512S, Isolated 1W regulated single output DC/DC converter
61 PA6/HD6 DSR, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
62 PA7/HD7 RTS, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
63 /W//REQA/PC5 WREQA, N/C
64 /DTR//REQA/PC3 DTRA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
65 /MWR/PC2//RTSA /MWR, Common memory bus signal
66 /CTSA/PC1 CTSA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
67 /DCDA/PC0 DCDA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
68 /SYNCA/PC4 SYNCA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
69 /RTXCA ?
70 VSS ---
71 /IOCS/IEO /IOCS, Logic circuit with M1, generates LIVE which conditions inputs
to the floppy disk controller
72 IEI IEI, J1 DIN48 pin 14C
73 VDD ---
74 RXDA RXDA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
75 /TRXCA ?
76 TXDA TXDA, U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
77 /DCDB//HRD DCDB, pulled high (U16), 20-pin P14, pin 12
78 /CTSB//HWR DCDB, pulled high (U17), 20-pin P14, pin 11
79 TXDB//HDDIS TXDB, 20-pin P14, pin 14
80 /TRXCB/HA0 TRXCB, pulled high (U17), 20-pin P14, pin 15
81 RXDB/HA1 RXDB, pulled high (U16), 20-pin P14, pin 16
82 /RTXCB/HA2 RTXCB, pulled high (U17), 20-pin P14, pin 17
83 /SYNCB//HCS SYNCB, pulled high (U16), 20-pin P14, pin 18
84 /HALT ?
85 /RFSH ?
86 /IORQ /IORQ, J1 DIN48 pin 12A
87 /MRD//MREQ /MRD, Common memory bus signal
88 E E, Conditions inputs to floppy disk controller; also J1 DIN48 pin 13B
89 /M1 /M1, Logic circuit with /IOCS, generates LIVE which conditions inputs
to the floppy disk controller; also J1 DIN48 pin 11A
90 /WR /WR, Common memory bus; Conditions inputs to floppy disk controller;
also J1 DIN48 pin 12C
91 /RD /RD, J1 DIN48 pin 11C
92 PHI PHI, J1 DIN48 pin 15B
93 VSS ---
94 XTAL 16 MHz XTAL
95 EXTAL 16 MHz XTAL
96 /WAIT /WAIT, J1 DIN48 pin 11B
97 /BUSACK ?
98 /BUSREQ /BUSREQ, Pulled high
99 /RESET /RST (to lots of places)
100 /NMI /NMI, Pulled high
P112 Serial Console
===================
The UARTs are not used on the P112 board (the UART signals are avaiable off-board through P14).
The serial console is provided by U7 LT1133, Advanced Low Power 5V RS232 Driver/Receiver
that connects to the P112 via the Z85230 ESCC channel A.
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