TMPR4925 datasheet(119/590 Pages) TOSHIBA

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Chapter 7 External Bus Controller

7-9

7.3.6

Access Modes

The following four modes are available as controller access modes. These modes can be set

separately for each channel.

•

Normal mode

•

Page mode

•

External ACK mode

•

Ready mode

Depending on the combination of modes in each channel, either of two modes in which the

ACK*/Ready signal operates differently (ACK*/Ready Dynamic mode, ACK*/Ready Static mode) is

selected by the ACK*/Ready Mode bit (PCFG.ACKIN) of the Chip Configuration Register. The mode

selected is applied globally to all channels.

(1) ACK*/READY Dynamic mode (PCFG.ACKIN = 0)

This mode is selected in the initial state.

The ACK*/Ready signal automatically switches to either input or output according to the setting of

each channel. When in the Normal mode or the Page mode, the ACK*/Ready signal is an output

signal, and the internally generated ACK* signal is output. When in the External ACK* or Ready

mode, the ACK*/Ready signal becomes an input signal. The ACK*/Ready signal outputs High if

there is no access to the External Bus Controller. However, this signal may output Low during

access to SDRAM.

Please refer to the timing diagrams (Figure 7.5.23 and Figure 7.5.24) and be careful to avoid

conflicts when switching from output to input.

(2) ACK*/Ready Static mode (PCFG.ACKIN = 1)

The internally generated ACK* signal is not output when in either the Normal mode or Page mode.

Therefore, the ACK*/Ready signal will not become an output in any channel.

Access using Burst transfer by the internal bus (G-Bus) is supported when in a mode other than the

Ready mode. However, the Ready mode is not supported.

Table 7.3.7 Operation Mode

RDY

EACK

Mode

ACK*/READY

Pin State

Access End

Timing State

G-Bus Burst

Access

0Normal

Output

Internally

Generated ACK*

√

External ACK*

Input

ACK* Input

√



READY

Input

Ready Input



Page

Output

Internally

Generated ACK*

√

ACK*/Ready

Dynamic Mode



Reserved





0Normal

Hi-Z

Internally

Generated ACK*

√

External ACK*

Input

ACK* Input

√



READY

Input

Ready Input



Page

Hi-Z

Internally

Generated ACK*

√

ACK*/Ready

Static Mode



Reserved





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