HD64F2149 Datasheet, PDF (103/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

Sleep Mode: A transition to sleep mode is made if the SLEEP instruction is executed while the
software standby bit (SSBY) in the standby control register (SBYCR) and the LSON bit in the
low-power control register (LPWRCR) are both cleared to 0. In sleep mode, CPU operations stop
immediately after execution of the SLEEP instruction. The contents of CPU registers are retained.
Software Standby Mode: A transition to software standby mode is made if the SLEEP
instruction is executed while the SSBY bit in SBYCR is set to 1 and the LSON bit in LPWRCR
and the PSS bit in the WDT1 timer control/status register (TCSR) are both cleared to 0. In
software standby mode, the CPU and clock halt and all MCU operations stop. As long as a
specified voltage is supplied, the contents of CPU registers and on-chip RAM are retained. The
I/O ports also remain in their existing states.
Hardware Standby Mode: A transition to hardware standby mode is made when the STBY pin
goes low. In hardware standby mode, the CPU and clock halt and all MCU operations stop. The
on-chip supporting modules are reset, but as long as a specified voltage is supplied, on-chip RAM
contents are retained.
2.9 Basic Timing
2.9.1 Overview
The CPU is driven by a system clock, denoted by the symbol ø. The period from one rising edge
of ø to the next is referred to as a “state.” The memory cycle or bus cycle consists of one, two, or
three states. Different methods are used to access on-chip memory, on-chip supporting modules,
and the external address space.
2.9.2 On-Chip Memory (ROM, RAM)
On-chip memory is accessed in one state. The data bus is 16 bits wide, permitting both byte and
word transfer instruction. Figure 2.17 shows the on-chip memory access cycle. Figure 2.18 shows
the pin states.
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