UPD6708 datasheet(26/72 Pages) NEC

26 / 72 page

µPD6708

4.2.2

Switching through software control

With the C/D pin at the high level and the R/W pin at the low level, the host interface mode can be switched from the

host controller by setting bits 5 and 4 of CMR to the values shown in Table 4-5.

Table 4-5. Switching Host Interface Mode by Software Control

Bit 5

Bit 4

Host Interface Mode

Mode switching by pin control

Data write mode

Data read mode

Status read mode

After one byte of data has been forwarded, the host interface mode will become the command write mode, which is

controlled by the C/D and R/W pins.

Figure 4-3. Example of Host Controller Connections by Software Control

IEBus

120

Ω

120

Ω

5 V

12 MHz

5 V

Power Supply

Voltage Detection

Circuit

PD6708

VDD

AVDD

BUS+

BUS–

GND

TEST

SCK

IRQ

C/D

R/W

RESET

SCK

INT

Host Controller

5 V

UPD6708 数据表(PDF) 26 Page - NEC

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