MC68HC711PH8 Motorola, MC68HC711PH8 Datasheet - Page 39

• Manufacturer Part Number: MC68HC711PH8
• Description: High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit
• Manufacturer: Motorola

2.8
During reset, MODA and MODB select one of the four operating modes. Refer to Section 3.
After the operating mode has been selected, the LIR pin provides an open-drain output (driven
low) to indicate that execution of an instruction has begun. In order to detect consecutive
instructions in a high-speed application, this signal drives high for a short time to prevent false
triggering. A series of E clock cycles occurs during execution of each instruction. The LIR signal
goes low during the first E clock cycle of each instruction (opcode fetch). This output is provided
for assistance in program debugging and its operation is controlled by the LIRDV bit in the OPT2
register.
The VSTBY pin is used to input RAM stand-by power. The MCU is powered from the VDD pin
unless the difference between the level of VSTBY and VDD is greater than one MOS threshold
(about 0.7 volts). When these voltages differ by more than 0.7 volts, the internal 1024-byte RAM
and part of the reset logic are powered from VSTBY rather than VDD. This allows RAM contents
to be retained without VDD power applied to the MCU. Reset must be driven low before V
removed and must remain low until V
2.9
These pins provide the reference voltages for the analog-to-digital converter.
2.10
This pin provides two separate functions, depending on the operating mode. In single chip and
bootstrap modes, PG7/R/W acts as input/output port G bit 7. Refer to Section 4 for further information.
In expanded and test modes, PG7/R/W performs the read/write function. PG7/R/W signals the
direction of transfers on the external data bus. A high on this pin indicates that a read cycle is in
progress.
MC68HC11PH8
MODA and MODB (MODA/LIR and MODB/VSTBY)
VRH and VRL
PG7/R/W
Figure 2-7 RAM stand-by connections
V
4.8 V NiCd
DD
(+)
DD
PIN DESCRIPTIONS
has been restored to a valid level.
V
V
DD
BATT
MAX 690
V
OUT
4.7k
To MODB/VSTBY
pin of M68HC11
MOTOROLA
DD
TPG
2-13
is
2