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3 a20 gate, Figure 15.2 typical lframe timing – Renesas H8S/2111B User Manual

Page 432

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Rev. 1.00, 05/04, page 398 of 544

The timing of the

LFRAME, LCLK, and LAD signals is shown in figures 15.2 and 15.3.

ADDR

Start

LFRAME

LAD3–LAD0

Number of clocks

LCLK

TAR

Sync

Data

TAR

Start

Cycle type,
direction,
and size

1

1

4

1

2

2

2

1

Figure 15.2 Typical

LFRAME Timing

ADDR

Start

LFRAME

LAD3–LAD0

LCLK

TAR

Sync

Cycle type,
direction,
and size

Slave must stop driving

Too many Syncs
cause timeout

Master will
drive high

Figure 15.3 Abort Mechanism

15.4.3 A20

Gate

The A20 gate signal can mask address A20 to emulate an addressing mode used by personal
computers with an 8086*-family CPU. A regular-speed A20 gate signal can be output under
firmware control. The fast A20 gate function that is speeded up by hardware is enabled by setting
the FGA20E bit to 1 in HICR0.

Note: An Intel microprocessor

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