SM5K3 Datasheet, PDF (14/28 Pages) Sharp Electrionic Components – 4-Bit Single-Chip Microcomputers(Controllers With 10-Bit A/D Converter)

SM5K3/SM5K4/SM5K5
FUNCTIONAL DESCRIPTION
Hardware Reset Function
Reset function initializes the SM5K3/5K4/5K5
systems. When the input on the RESET pin goes
Low, the system enters reset condition after 2
command cycles. After the RESET pin goes High
level, the reset condition is removed as the input
pulse from OSCIN pin repeats 2¹⁵ times, forcing the
program counter to start at 0 page and 0 address.
Initialized status of the system immediately after
resetting is shown below.
Table 2 Status of Flags and Registers Immediately after Reset
FLAG REGISTER
PC
SP
RAM
Register A
Register X
P0, P2, P4, P5 output latch register
Timers (RA, RB), divider
STATUS
0
Level 1
Undefined
Undefined
Undefined
0
0
FLAG REGISTER
IFA flag
IFB flag
IFT flag
IME flag
C flag
BM, BL registers, SB register
R3, R8∗, R9, RC, RE, RF
∗ The content of the bit R84 is undefined because it is read only.
STATUS
0
0
0
0
Undefined
Undefined
0
Reset causes the following changes.
1) I/O pins are set input.
2) All mode registers are reset.
3) Output latch register P0 is reset, causing P00 to
P03 pins go High level.
4) Interrupt request flags (IFA, IFB, and IFT),
interrupt master enable flag (IME) are reset,
disabling all interrupts.
Standby Feature
The standby function saves power by stopping the
program whenever it is not necessary to run. The
mode in which the microcomputer is executing the
program is called the run mode and the mode in
which it stops the program is called the standby
mode. Standby mode is further divided into two
modes : stop mode and halt mode, one of which is
selected by halt instruction or stop instruction. Upon
removal of standby condition, the SM5K3/5K4/5K5
return from the standby mode to the normal run
mode. To enter the standby mode, select either
stop mode or halt mode whichever is appropriate
(Fig. 8).
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