View source for NC 100/150/200 IO Specification

This update to NCIOSPEC.TXT covers the differences between the NC100 hardware
(documented in the original NCIOSPEC.TXT below) and the NC150/NC200 hardware.

This information was discovered mainly by Russell Marks during development of his
NC emulator and ZCN software, with the remaining information found by myself
during development of my NC200 emulation for M.E.S.S.

This update does not cover the NC150. I do not have details of any differences between this and the NC100 at this time.

When I have information on this system, it will be documented here.

These have been worked out by dissassembling the rom, and looking at patterns
of I/O read/writes.

* The NC200 does not have a TC8521 Real Time Clock, instead it has a MC146818 Real Time Clock. The MC146818 is no longer produced now, but is part of many PC designs.

* The NC200 has a [[NEC765]] compatible floppy disc controller. The disc interface was designed by Ranger Computers.

The ports listed in this section are different or have additional
information to the NC100 port definitions. The other ports have the same
function as the NC100.


* The NC100 clock speed is 4.606MHz, at this time it is unknown if the NC200 has a different clock speed.

* The NC100 on/off button generates an NMI.
* The NC200 on/off button generates a maskable interrupt.

Keyboard NC100:

 B0: 
 bit 0: Shift (Left)
 bit 1: Shift (Right)
 bit 2: unused
 bit 3: Cursor Left (Red)
 bit 4: Return
 bit 5: unused
 bit 6: unused
 bit 7: unused

 B1:
 bit 0: Function (Yellow)
 bit 1: Control
 bit 2: Stop
 bit 3: Space
 bit 4: unused
 bit 5: unused
 bit 6: 5
 bit 7: unused
 
 B2: 
 bit 0: Caps Lock
 bit 1: Symbol
 bit 2: 1
 bit 3: Tab
 bit 4: unused
 bit 5: unused
 bit 6: unused
 bit 7: unused

 B3:
 bit 0: 3
 bit 1: 2
 bit 2: Q
 bit 3: W
 bit 4: E
 bit 5: unused
 bit 6: S
 bit 7: D

 B4:
 bit 0: 4
 bit 1: unused
 bit 2: Z
 bit 3: X
 bit 4: A
 bit 5: unused
 bit 6: R
 bit 7: F
 
 B5:
 bit 0: B
 bit 1: V
 bit 2: T
 bit 3: Y
 bit 4: G
 bit 5: C

 B6:
 bit 0: 6
 bit 1: Cursor Down (Blue)
 bit 2: Del
 bit 3: Cursor Right (Green)
 bit 4: \
 bit 5: /
 bit 6: H
 bit 7: N

 B7:
 bit 0: =
 bit 1: 7 
 bit 2: ~
 bit 3: Up
 bit 4: Menu
 bit 5: U
 bit 6: M
 bit 7: K

 B8:
 bit 0: 8
 bit 1: -
 bit 2: )
 bit 3: (
 bit 4: "
 bit 5: I
 bit 6: J
 bit 7: ,

 B9:
 bit 0: 0
 bit 1: 9
 bit 2: Del
 bit 3: P
 bit 4: :
 bit 5: L
 bit 6: O
 bit 7: STOP




 Address                 Comment                 	R/W 
 =======                 =======                 	===

 00			Display Memory start		W
 20			Memory card wait state		W
 A0			Card Battery status		R
 60			Interrupt Request Mask		W
 70			on/off control			W		
 80			Printer Status			R					
 90			IRQ Status			R
 B0-B9			Key data in			R
 D0-D1			MC146818 Real Time Clock	R/W
 E0	                NEC765 Status          		R
 E1			NEC765 Data			R/W


Address = 00                                    Write only
start address of display memory


 bit 7           A15
 bit 6           A14
 bit 5           A13
 bits 4-0        Not Used

Address = 20                                    Write only
Memory card wait state control
	
 bit 7: memory card wait state control:  1 for wait states, 0 for no wait
 bit 0: NEC765 Terminal Count input (1=TC active, 0=TC inactive)

Address = 30                                    Write only
Floppy motor control
	
 bit 3: Floppy motor: 1=off, 0=on

Address = 70
on/off control


 bit 2: Backlight: 1=off, 0=on
 bit 0: on/off control: 1 = on, 0 = off


Address = 80
centronics status

 bit 0: busy state

Address = A0
Card battery status


 bit 7: memory card present 0 = yes, 1 = no
 bit 6: memory card write protected 1 = yes, 0 = no
 bit 5: lithium battery 0 if >= 2.7 volts
 bit 4: input voltage = 1, if >= to 4 volts
 bit 3: ** unknown use **
 bit 2: alkaline batteries. 0 if >=3.2 volts
 bit 1: ** unknown use **
 bit 0: battery power: if 1: batteries are too low for disk usage, if 0: batteries ok for disc usage

Address = B0 - B9                                 Read only
Keyboard data


 B0..B9          each key of the 64 on the keyboard
                        will set a bit in one of these bytes
                        while pressed.

Russell Marks confirms that reading B9 does not clear the key scan interrupt
like it does on the NC100. The interrupt must be explicitly cleared!

Address = 60                                    Write only
Interrupt request mask


 bit 7:		** unknown use **
 bit 6: 		** unknown use ** (Real Time Clock Alarm?)
 bit 5:		NEC765 FDC
 bit 4:		Power off interrupt
 bit 3           Key scan
 bit 2           TC8251 Serial Interrupt (Tx Ready OR Rx Ready)
 bit 1           ** unknown use ** (not checked by OS - not used?)
 bit 0           ACK from parallel interface

Address = 80
Printer status

 bit 7..1:	* unknown use *
 bit 0:		printer busy status
			1 = busy

Address = 90                                     Read/Write
IRQ status


 bit 7:		** unknown use **
 bit 6: 		** unknown use ** (Real Time Clock Alarm?)
 bit 5:		NEC765 FDC
 bit 4:		Power off interrupt
 bit 3           Key scan
 bit 2           TC8251 Serial Interrupt (Tx Ready OR Rx Ready)
 bit 1           ** unknown use ** (not checked by OS - not used?)
 bit 0           ACK from parallel interface
 

Address = D0/D1                                    
MC146818 Real Time Clock	

Consult MC146818 datasheet.


Address = E0/E1                                    
NEC765 floppy disc controller	

Consult NEC765 datasheet.

Read:

 E0 = Status, 
 E1 = data

Write:

 E0 = not used, 
 E1 = data

[http://groups.google.com/group/comp.sys.amstrad.8bit/browse_thread/thread/ce201414eff39a29/19cb6f7056d49480?lnk=gst&q=nc100+sound#19cb6f7056d49480  Russell Marks's notes about sound generation on NC100]

[[NC100 IO Specification]]

[[Category:NC Series]]