Datasheet

Section 6 Bus Controller (BSC)
R01UH0310EJ0500 Rev. 5.00 Page 209 of 1384
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
6.6.3 Data Bus
The bus width of the address/data multiplexed I/O space can be specified for either 8-bit access
space or 16-bit access space by the ABW7 and ABW6 bits in ABWCRA. For the 8-bit access
space, AD15 to AD8 are valid for both address and data. For the 16-bit access space, AD15 to
AD0 are valid for both address and data. If the address/data multiplexed I/O space is accessed, the
corresponding address will be output to the address bus. For details on access size and data
alignment, see section 6.5.1, Data Size and Data Alignment.
6.6.4 Address Hold Signal
In the address/data multiplexed I/O space, a hold signal (AH) that indicates the timing for latching
the address is output. The AH output pin is multiplexed with the AS output pin. When the external
address space is specified as the address/data multiplexed I/O space, the multiplexed pin functions
as the AH output pin. Note however that the multiplexed pin will function as the AS output pin
until the address/data multiplexed I/O space is specified.
6.6.5 Basic Timing
The bus cycle in the address/data multiplexed I/O interface consists of an address cycle and a data
cycle. The data cycle is based on the basic bus interface timing specified by ABWCR, ASTCR,
WTCRAH, RDNCR, and CSACR.
(1) 8-Bit, 2-State Data Access Space
Figure 6.21 shows the bus timing for an 8-bit, 2-state data access space. When an 8-bit access
space is accessed, the upper halves (AD15 to AD8) of both the address bus and data bus are used.
Wait states cannot be inserted in the data cycle.