M37536M4 Datasheet, PDF (35/45 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
7536 Group
NOTES ON PROGRAMMING
Processor Status Register
The contents of the processor status register (PS) after reset are
undefined except for the interrupt disable flag I which is “1”. After
reset, initialize flags which affect program execution. In particular, it
is essential to initialize the T flag and the D flag because of their
effect on calculations.
Interrupts
The contents of the interrupt request bit do not change even if the
BBC or BBS instruction is executed immediately after they are
changed by program because this instruction is executed for the pre-
vious contents. For executing the instruction for the changed con-
tents, execute one instruction before executing the BBC or BBS in-
struction.
Decimal Calculations
• For calculations in decimal notation, set the decimal mode flag D to
“1”, then execute the ADC instruction or SBC instruction. In this
case, execute SEC instruction, CLC instruction or CLD instruction
after executing one instruction following the ADC instruction or SBC
instruction.
• In the decimal mode, the values of the N (negative), V (overflow)
and Z (zero) flags are invalid.
Timers
• When n (0 to 255) is written to a timer latch, the frequency division
ratio is 1/(n+1).
• When a count source of timer X is switched, stop a count of timer X.
Ports
• The values of the port direction registers cannot be read.
That is, it is impossible to use the LDA instruction, memory opera-
tion instruction when the T flag is “1”, addressing mode using di-
rection register values as qualifiers, and bit test instructions such
as BBC and BBS.
It is also impossible to use bit operation instructions such as CLB
and SEB and read/modify/write instructions of direction registers
for calculations such as ROR.
For setting direction registers, use the LDM instruction, STA in-
struction, etc.
• Set "1" to each bit 6 of the port P3 direction register and the port P3
register (for only 7532 Group).
A-D Converter
The comparator uses internal capacitors whose charge will be lost if
the clock frequency is too low.
Make sure that f(XIN) is 500kHz or more during A-D conversion.
Do not execute the STP instruction during A-D conversion.
Instruction Execution Timing
The instruction execution time can be obtained by multiplying the
frequency of the internal clock φ by the number of cycles mentioned
in the machine-language instruction table.
The frequency of the internal clock φ is the same as that of the XIN in
double-speed mode, twice the XIN cycle in high-speed mode and 8
times the XIN cycle in middle-speed mode.
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
NOTES ON USE
Handling of Power Source Pin
In order to avoid a latch-up occurrence, connect a capacitor suitable
for high frequencies as bypass capacitor between power source pin
(Vcc pin) and GND pin (Vss pin). Besides, connect the capacitor to
as close as possible. For bypass capacitor which should not be lo-
cated too far from the pins to be connected, a ceramic capacitor of to
0.1 µF is recommended.
Handling of USBVREFOUT Pin
In order to prevent the instability of the USBVREFOUT output due to
external noise, connect a capacitor as bypass capacitor between
USBVREFOUT pin and GND pin (VSS pin). Besides, connect the ca-
pacitor to as close as possible. For bypass capacitor, a ceramic or
electrolytic capacitor of 0.1 µF is recommended.
One Time PROM Version
The CNVss pin is connected to the internal memory circuit block by a
low-ohmic resistance, since it has the multiplexed function to be a
programmable power source pin (VPP pin) as well.
To improve the noise reduction, connect a track between CNVss pin
and Vss pin with 1 to 10 kΩ resistance.
The mask ROM version track of CNVss pin has no operational inter-
ference even if it is connected via a resistor.
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