Renesas ZTAT H8S/2357F, Hardware Manual

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Rev.6.00 Oct.28.2004 page 546 of 1016
REJ09B0138-0600H
16.3 Interface to Bus Master
ADDRA to ADDRD are 16-bit registers, and the data bus to the bus master is 8 bits wide. Therefore, in accesses by the
bus master, the upper byte is accessed directly, but the lower byte is accessed via a temporary register (TEMP).
A data read from ADDR is performed as follows. When the upper byte is read, the upper byte value is transferred to the
CPU and the lower byte value is transferred to TEMP. Next, when the lower byte is read, the TEMP contents are
transferred to the CPU.
When reading ADDR. always read the upper byte before the lower byte. It is possible to read only the upper byte, but if
only the lower byte is read, incorrect data may be obtained.
Figure 16-2 shows the data flow for ADDR access.
Bus master
(H'AA)
ADDRnH
(H'AA)
ADDRnL
(H'40)
Lower byte read
ADDRnH
(H'AA)
ADDRnL
(H'40)
TEMP
(H'40)
TEMP
(H'40)
(n = A to D)
(n = A to D)
Module data bus
Module data bus
Bus interface
Upper byte read
Bus master
(H'40)
Bus interface
Figure 16-2 ADDR Access Operation (Reading H'AA40)
16.4 Operation
The A/D converter operates by successive approximation with 10-bit resolution. It has two operating modes: single mode
and scan mode.
16.4.1 Single Mode (SCAN = 0)
Single mode is selected when A/D conversion is to be performed on a single channel only. A/D conversion is started when
the ADST bit is set to 1, according to the software or external trigger input. The ADST bit remains set to 1 during A/D
conversion, and is automatically cleared to 0 when conversion ends.