BD8132FV, BD8139AEFV

Technical Note

10/20

www.rohm.com

2009.07 - Rev.B

© 2009 ROHM Co., Ltd. All rights reserved.

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Auto-read function

The auto-read function enables the IC's 1 kbit microwire type external memory to be automatically read.

This block operates in synchronization with the external input CLK's falling edge to output the external memory chip select

signal CS as well as the memory read data signal MEMDO.

The read data signal consists of a start bit for the external memory, a read code, and a read address. When this signal is sent

to the external memory, the memory outputs the data corresponding to the indicated address. Data output from the memory

is read from the MEMDI pin, and this block automatically generates the serial DATA and LATCH signals and writes the

memory data to the register. Memory reads are synchronized to the CLK's falling edge.

Read addresses start from address 00H and repeat until address 12H, so data must be stored from address 00H to address 12H.

The auto-read function is controlled using the R/W signal. Read access to the external memory is performed continuously

while the R/W signal is low. To access the external memory from another device, the R/W signal must be set to high. When

the R/W signal is set to high, the CS and MEMDO pins enter a high-impedance state.

Fig. 23 Auto-read Timing Chart

Fig. 24 External Memory Data Table

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Serial communications timing chart

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Auto-read timing chart

Fig.25

Fig.26

SDIN

LATCH

CLK

tLC

tSC

tWL

tWH

tCL

tLA

R/W

C

tRC

tRW

MEMDO

CS

MEMDI

tCDO

tCCS

tDIC

tCR

High-impedance

High-impedance

Auto-read timing

R/W

CS

CLK

MEMDO

Address 00H

Start bit and read code

Address 01H

MEMDI

Memory data

D15 to D0

INTERNAL

DATA

D15 to D0

INTERNAL

LATCH

External m emory data format

MSB

LSB

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

d1

d2

d3

d4

d5

d6

d7

d8

d9

d10

d11

d12

d13

d14

d15

d16

OSC

mode

Register address

DAC data