Register; Standby Control Register (Sbycr) - Hitachi SH7032 Hardware Manual

19.1.2

Register

Table 19.2 summarizes the register related to the power-down state.
Table 19.2 Standby Control Register (SBYCR)
Name
Standby control register
Note: Only the values of bits A27–A24 and A8–A0 are valid; bits A23–A9 are ignored. For
*
details on the register addresses, see section 8.3.5, Area Descriptions.
19.2

Standby Control Register (SBYCR)

The standby control register (SBYCR) is an 8-bit read/write register. It is used to enter standby
mode and also sets the port states in standby mode. SBYCR is initialized to H'1F by a reset.
Bit:
Bit name:
Initial value:
R/W:
• Bit 7 (Standby (SBY)): SBY enables transition to standby mode. The SBY bit cannot be set to
1 while the timer enable bit (bit TME) in timer control/status register TCSR of the watchdog
timer (WDT) is set to 1. To enter standby mode, clear the TME bit to 0 to halt the WDT and
then set the SBY bit.
SBY Description
0 Executing SLEEP instruction puts the chip into sleep mode
1 Executing SLEEP instruction puts the chip into standby mode
• Bit 6 (Port High-Impedance (HIZ)): HIZ selects whether I/O ports remain in their previous
states during standby, or are placed in the high-impedance state when standby mode is entered.
The HIZ bit cannot be set to 1 while the TME bit is set to 1. To place the pins of the I/O ports
in high impedance, clear the TME bit to 0 before setting the HIZ bit.
HIZ Description
0 Port states are maintained during standby
1 Ports are placed in the high-impedance state in standby
• Bits 5–0 (Reserved): Bit 5 is a read-only bit that is always read as 0. Only write 0 in bit 5.
Writing to bits 4–0 is disabled. These bits are always read as 1.
460
Abbreviation
SBYCR
7 6
SBY HIZ —
0 0
R/W R/W —
R/W Initial Value Address*
R/W H'1F
5 4 3
— —
0 1 1
— —
Access size
H'5FFFFBC 8, 16, 32
2 1
— —
1 1
— —
(Initial value)
(Initial value)
0
—
1
—