SH7041A datasheet(613/923 Pages) RENESAS

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16.3

Interface with CPU

Although A/D data register ADDR (ADDRA0–ADDRD0, ADDRA1–ADDRD1) are 16-bit

registers, the bus width within the chip that integrates with the CPU is 8-bits. So, upper and lower

data of the ADDR must be read separately.

To avoid change in data while reading the upper/lower 2 bytes of ADDR, the lower byte data is

read through the temporary register (TEMP). The upper byte data can be read directly.

The procedure for reading data from ADDR is as follows: First, read the upper byte data from

ADDR. At this time, the upper byte data is read directly into the CPU and the lower byte data is

transferred to TEMP of the mid-speed A/D converter. Next, read the lower byte to read the TEMP

contents into the CPU.

When reading the ADDR in byte size, read the upper byte before the lower byte. Furthermore, it is

possible to read only the upper byte, however, please note that contents are not guaranteed when

reading only the lower byte. In addition, when reading ADDR in word size, upper byte is

automatically read before the lower byte.

Figure 16.2 shows the data flow when reading from ADDR.

CPU

(H'AA)

ADDRnH

(H'AA)

ADDRnL

(H'40)

TEMP

(H'40)

CPU

(H'40)

ADDRnH

(H'AA)

ADDRnL

(H'40)

TEMP

(H'40)

Bus interface

Module data bus

Bus interface

Module data bus

Figure 16.2 ADDR Access Operation (During Reading of (H'AA40))

SH7041A Datasheet(PDF) 613 Page - Renesas Technology Corp