Sharp MZ-3500 service manual 0001, Main CPU \m, MZ3500, Sub CPU and I/O port, 0000

MZ3500

3-3. Sub CPU and I/O port

			J	s07 *.
	AS6		5
			~9	S06
	ASS	2	Y6
			_JQ	SOS ^
SUB	AS4	i	J	r CKP 1 . CSP 2

CPU	.Jl	SO4 ^
4G	Y 4
AST 4_	012	S03 ,. -^
*""

Shown at the left is the circuit used by the CPU to select the I/O ports The out put address from the sub CPU is decoded by the 74LS138to create the select signal. Shown below is the address map and select signals.

AS 7654 M£X\

0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

	5	D15 S°2		HEC3 -C*
"MT
	6	14	"SOT	-^
	Gl	Yl
		YO D15	'*°°	r MAIN CPU \m

74LS138

8	8	8
8		Signal description
1 2 3 4 5 6 7 8 9 A B C D E F
soo		Output signal to set the flipflop to apply interrupt (INTO) to the
		main CPU. Enables communication between CPU's.
		8251 SIO chip select.
S018251		ASO is used for data control selection.
		AS1, AS2, and ASS are "don't care".
		8253 counter chip select.
S02 8253		ASO and AS1 are used for programming during write.
		AS2 and ASS are "don't care".
		8255 PIO chip select.
S03 8255		ASO and AS1 are used for port/control selection.
		AS2 and ASS are "don't care".
		8-bit input port.
S04 input port select		Used for read.
		AS3 are "don't care".
		CRT control I/O port chip select.
805		AS1, AS2, and ASS are used for write.
		ASO is "don't care".
		UPD7220 (graphic) chip select.
S06		ASO is used for read and write.
		AS1, AS2, and AS3 are "don't care"
		UPD7220 (character) chip select.
S07		ASO is used for read and write.
		AS1, AS2, and AS3 are "don't care"

NOT USE

- 18-