TMPR4937 datasheet(57/552 Pages) TOSHIBA

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Chapter 3 Signals

3-3

3.1.3

External Interface Signals

Table 3.1.3 External Interface Signals

Signal Name

Type

Description

Initial State

SYSCLK

Output

System Clock

Clock for external I/O devices.

Outputs a clock in full speed mode (at the same frequency as the G-Bus clock

(GBUSCLK) frequency), half speed mode (at one half the GBUSCLK frequency), third

speed mode (at one third the GBUSCLK frequency), or quarter speed mode (at one

quarter the GBUSCLK frequency). The boot configuration signals on the ADDR[14:13]

pins select which speed mode will be used.

When this clock signal is not used, the pin can be set to H using the SYSCLK Enable

bit of the configuration register (CCFG.SYSCLKEN).

High

ACE*

Output

Address Clock Enable

Latch enable signal for the high-order address bits of ADDR.

High

CE[7:0]*

Output

Chip Enable

Chip select signals for ROM, SRAM, and I/O devices (refer to Section “3.3 Pin

multiplex”).

All High

OE*

Output

Output Enable

Output enable signal for ROM, SRAM, and I/O devices.

High

SWE*

Output

Write Enable

Write enable signal for SRAM and I/O devices.

High

BWE[3:0]*

/BE[3:0]*

Output

Byte Enable/Byte Write Enable

BE[3:0]* indicate a valid data position on the data bus DATA[31:0] during read and

write bus operation. In 16-bit bus mode, only BE[1:0]* are used. In 8-bit bus mode,

only BE[0]* is used.

BWE[3:0]* indicate a valid data position on the data bus DATA[31:0] during write bus

operation. In 16-bit bus mode, only BWE[1:0]* are used. In 8-bit bus mode, only

BWE[0]* is used.

The following shows the correspondence between BE[3:0]*/BWE[3:0]* and the data

bus signals.

BE[3]*/BWE[3]*:

DATA[31:24]

BE[2]*/BWE[2]*:

DATA[23:16]

BE[1]*/BWE[1]*:

DATA[15:8]

BE[0]*/BWE[0]*:

DATA[7:0]

The boot configuration signal on the DATA[5] pin and the EBCCRn.BC bit of the

external bus controller determine whether the signals are used as BE[3:0]* or

BWE[3:0]*.

All High

ACK*/ READY Input/output

Data Acknowledge/Ready

Flow control signal (refer to Section “7.3.6 Access Modes”).

High

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