PIA - Revision history

TomHarte: Expand details on connections.

2026-05-18T15:25:58Z

Expand details on connections.

@@ Line 1: / Line 1: @@
 The '''Peripheral Interface Adapter''', formally the Motorola 6821, is a chip that provides two ports of parallel input and output plus control lines and interrupts. There are two in your CoCo, usually referred to as PIA0 and PIA1, and they're responsible for keyboard and joystick input, sound output and video mode selection and interrupt generation, amongst other tasks.
 === Keyboard ===
-The keyboard can be scanned through PIA0 via addresses $FF00 and $FF02. The first address ($FF00) represents keyboard rows as well as joystick buttons, and the second address ($FF02) keyboard columns; programs will normally set one of these as output and one of these as inputs, most normatively configuring $FF02 as output and using it to select which columns to scan and then reading $FF00 as input to very which rows on those selected columns had keys pressed. [[Color Basic]], when running a prompt, converts these to ASCII values to be printed to the screen at cursor position.
+The keyboard can be scanned through PIA0 via addresses $FF00 (PIA0 port A data) and $FF02 (port B data). The first address ($FF00) represents keyboard rows as well as joystick buttons, and the second address ($FF02) keyboard columns; programs will normally set one of these as output and one of these as inputs, most normatively configuring $FF02 as output and using it to select which columns to scan and then reading $FF00 as input to very which rows on those selected columns had keys pressed. [[Color Basic]], when running a prompt, converts these to ASCII values to be printed to the screen at cursor position.
 These two value correspond to ASCII values according to the following table:

TomHarte: /* Keyboard */ These are columns, not rows.

2026-05-18T14:46:01Z

Keyboard: These are columns, not rows.

← Older revision		Revision as of 10:46, 18 May 2026
Line 100:		Line 100:
	\|}		\|}

	Keyboard layout is one of the few areas of hardware difference between a CoCo and a Dragon, other than video standard; the Dragon has the same physical layout as the CoCo but changes the column numbering — columns 6 and 7 are the same as the CoCo but everything else is off by 2. E.g. the CoCo's ~~row~~ 0 is the Dragon's ~~row~~ 2, the Coco's ~~row~~ 4 is the Dragon's ~~row~~ 6 and the CoCo's ~~row~~ 5 is the Dragon's ~~row~~ 0.		Keyboard layout is one of the few areas of hardware difference between a CoCo and a Dragon, other than video standard; the Dragon has the same physical layout as the CoCo but changes the column numbering — columns 6 and 7 are the same as the CoCo but everything else is off by 2. E.g. the CoCo's column 0 is the Dragon's column 2, the Coco's column 4 is the Dragon's column 6 and the CoCo's column 5 is the Dragon's column 0.

	(under construction)		(under construction)

	[[Category:Hardware]]		[[Category:Hardware]]

TomHarte: Add some more detail, add keyboard map.

2026-05-18T14:44:51Z

Add some more detail, add keyboard map.

← Older revision		Revision as of 10:44, 18 May 2026
Line 1:		Line 1:
	The '''Peripheral Interface Adapter''' is a chip, of ~~which there~~ are two in your CoCo, ~~that is used~~ for ~~handling I/O~~, amongst other ~~things~~.		The '''Peripheral Interface Adapter''', formally the Motorola 6821, is a chip that provides two ports of parallel input and output plus control lines and interrupts. There are two in your CoCo, usually referred to as PIA0 and PIA1, and they're responsible for keyboard and joystick input, sound output and video mode selection and interrupt generation, amongst other tasks.

			=== Keyboard ===

	~~=== Keyboard ===~~		The keyboard can be scanned through PIA0 via addresses $FF00 and $FF02. The first address ($FF00) represents keyboard rows as well as joystick buttons, and the second address ($FF02) keyboard columns; programs will normally set one of these as output and one of these as inputs, most normatively configuring $FF02 as output and using it to select which columns to scan and then reading $FF00 as input to very which rows on those selected columns had keys pressed. [[Color Basic]], when running a prompt, converts these to ASCII values to be printed to the screen at cursor position.

	The keyboard can be scanned through PIA-1 by pulling two values from addresses $FF00 and $FF02. [[Color Basic]] ROM, when running a prompt, converts these to ASCII values to be printed to the screen at cursor position. The first address ($FF00) represents the keyboard rows as well as the joystick button, and the second address ($FF02) the keyboard columns. These two value correspond to ASCII values according to the following table:		These two value correspond to ASCII values according to the following table:

	{\| class="wikitable"		{\| class="wikitable"
Line 19:		Line 20:
	\|-		\|-
	\|0		\|0
	\|		\|@
	\|		\|H
	\|		\|P
	\|		\|X
	\|		\|0
	\|		\|8
	\|		\|Enter
	\|		\|
	\|-		\|-
	\|1		\|1
	\|		\|A
	\|		\|I
	\|		\|Q
	\|		\|Y
	\|		\|1
	\|		\|9
	\|		\|Clear
	\|		\|
	\|-		\|-
	\|2		\|2
	\|		\|B
	\|		\|J
	\|		\|R
	\|		\|Z
	\|		\|2
	\|		\|:
	\|		\|Break
	\|		\|
	\|-		\|-
	\|3		\|3
	\|		\|C
	\|		\|K
	\|		\|S
	\|		\|Up
	\|		\|3
	\|		\|;
	\|		\|
	\|		\|
	\|-		\|-
	\|4		\|4
	\|		\|D
	\|		\|L
	\|		\|T
	\|		\|Down
	\|		\|4
	\|		\|,
	\|		\|
	\|		\|
	\|-		\|-
	\|5		\|5
	\|		\|E
	\|		\|M
	\|		\|U
	\|		\|Left
	\|		\|5
	\|		\| -
	\|		\|
	\|		\|
	\|-		\|-
	\|6		\|6
	\|		\|F
	\|		\|N
	\|		\|V
	\|		\|Right
	\|		\|6
	\|		\|.
	\|		\|
	\|		\|
	\|-		\|-
	\|7		\|7
	\|		\|G
	\|		\|O
	\|		\|W
	\|		\|Space
	\|		\|7
	\|		\|/
	\|		\|Shift
	\|		\|
	\|}		\|}

			Keyboard layout is one of the few areas of hardware difference between a CoCo and a Dragon, other than video standard; the Dragon has the same physical layout as the CoCo but changes the column numbering — columns 6 and 7 are the same as the CoCo but everything else is off by 2. E.g. the CoCo's row 0 is the Dragon's row 2, the Coco's row 4 is the Dragon's row 6 and the CoCo's row 5 is the Dragon's row 0.

	(under construction)		(under construction)

	[[Category:Hardware]]		[[Category:Hardware]]

Polluks: Category

2015-09-10T21:21:39Z

Fedor Steeman: /* Keyboard */

2014-03-25T10:16:27Z

Keyboard

← Older revision		Revision as of 06:16, 25 March 2014
Line 3:		Line 3:

	=== Keyboard ===		=== Keyboard ===

			The keyboard can be scanned through PIA-1 by pulling two values from addresses $FF00 and $FF02. [[Color Basic]] ROM, when running a prompt, converts these to ASCII values to be printed to the screen at cursor position. The first address ($FF00) represents the keyboard rows as well as the joystick button, and the second address ($FF02) the keyboard columns. These two value correspond to ASCII values according to the following table:

			{\| class="wikitable"
			\|-
			\|
			\|0
			\|1
			\|2
			\|3
			\|4
			\|5
			\|6
			\|7
			\|-
			\|0
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|1
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|2
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|3
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|4
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|5
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|6
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|-
			\|7
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|
			\|}

	(under construction)		(under construction)

Fedor Steeman: Created page with "The '''Peripheral Interface Adapter''' is a chip, of which there are two in your CoCo, that is used for handling I/O, amongst other things. === Keyboard === (under constru..."

2014-03-25T09:45:29Z

Created page with "The '''Peripheral Interface Adapter''' is a chip, of which there are two in your CoCo, that is used for handling I/O, amongst other things. === Keyboard === (under constru..."

New page

The '''Peripheral Interface Adapter''' is a chip, of which there are two in your CoCo, that is used for handling I/O, amongst other things.

=== Keyboard ===

(under construction)

← Older revision		Revision as of 17:21, 10 September 2015
Line 100:		Line 100:

	(under construction)		(under construction)

			[[Category:Hardware]]