BUS INTERFACE UNIT

T2

T3

TW

T4

CLKOUT

1 2

ARDY

In a Normally-Ready system, a wait state will be inserted when 1 & 2 are met. (Assumes SRDY is low.)

1.TARYCH : ARDY low to clock high

2.TARYCHL : Clock high to ARDY high (ARDY inactive hold time)

T2

T3

TW

T4

CLKOUT

1 2

ARDY

SRDY

Alternatively, in a Normally-Ready system, a wait state will be inserted when1 & 2 are met for SRDY and ARDY.

1.TARYCL, TSRYCL : ARDY and SRDY low to clock low

2.TCHARX, TCLSRY : ARDY and SRDY low from clock low

!Failure to meet ARDY and SRDY setup and hold can cause a device failure (i.e., the bus hangs or operates inappropriately).

A1512-0A

Figure 3-18. Normally Ready System Timings

Conditions causing the BIU to become idle include the following.

The instruction prefetch queue is full.

An effective address calculation is in progress.

The bus cycle inherently requires idle states (e.g., interrupt acknowledge, locked opera- tions).

Instruction execution forces idle states (e.g., HLT, WAIT).

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Intel 80C188XL, 80C186XL user manual Normally Ready System Timings