Intel 80386 manual Data Bus do through, Address Bus BEO# through BE3#, A2 through A31

80386

2X CLOCK [		CLK2 ~			t\
				ADDRESS BUS	A2-A31
				BE3#	v
	<DATA BUS			BE2#	BYTE	32-BIT
32-BIT[DO_D31				BE1#		ADDRESS
					ENABLES
DATA
	~	v		BEO#	1
		ADS#		W/R#
		R~~~:~	80386	D/C#
BUS [			PROCESSOR	M/IO#
CONTROL				LOCK#
		HOLD ~		PEREQ
BUS{		HLDA		I~ BUSY#	} COPROCESSOR SIGNALLING
ARBITRATION				~ ERROR#
		INTR t>		Vee
INTERRUPTS {		NMI t>
		RESET t>		<l	} POWER CONNECTIONS
				GND
				<l
						231630-1
		Figure 5-1. Functional Signal Groups
			PROCESSOR CLOCK		PROCESSOR CLOCK
			PERIOD		PERIOD

CLK2 PERIOD CLK2 PERIOD CLK2 PERIOD CLK2 PERIOD

~1 ~2 ~1 ~2

CLK2 [

INTERNAL 80386

PROCESSOR CLOCK [ (SAME FREQUENCY AS

82384 CLK SIGNAL)

62 ns MIN}

(16 MHz MAX) 80386-16

83 ns MIN}

(12.5 MHz MAX) 80386-12

231630-2

Figure 5-2. CLK2 Signal and Internal Processor Clock

5.2.3 Data Bus (DO through 031)

These three-state bidirectional signals provide the general purpose data path between the 80386 and other devices. Data bus inputs and outputs indicate "1" when HIGH. The data bus can transfer data on 32- and 16-bit buses using a data bus sizing feature controlled by the 8S16# input. See section 5.2.6 Bus Conto!. Data bus reads require that read data setup and hold times t21 and t22 be met for correct operation. During any write operation (and during halt cycles and shutdown cycles), the 80386 always drives all 32 signals of the data bus even if the cur- rent bus size is 16-bits.

61

5.2.4Address Bus (BEO# through BE3#, A2 through A31)

These three-state outputs provide physical memory addresses or I/O port addresses. The address bus is capable of addressing 4 gigabytes of physical memory space (OOOOOOOOH through FFFFFFFFH), and 64 kilobytes of I/O address space (OOOOOOOOH through OOOOFFFFH) for programmed I/O. I/O transfers automatically generated for 80386-to-co- processor communication use I/O addresses 800000F8H through 800000FFH, so A31 HIGH in conjunction with M/IO# LOW allows simple genera- tion of the coprocessor select signal.