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APPENDIX
7540 Group User’s Manual
(7) Instruction Execution Timing
The instruction execution time can be obtained by multiplying the frequency of the internal clock f by
the number of cycles mentioned in the machine-language instruction table.
The frequency of the internal clock f 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.
(8) CPU Mode Register
The oscillation mode selection bit and processor mode bits can be rewritten only once after releasing
reset. However, after rewriting it is disable to write any value to the bit. (Emulator MCU is excluded.)
When a ceramic oscillation is selected, a double-speed mode of the clock division ratio selection bits
can be used. Do not use it when an RC oscillation is selected.
Fig. 3.3.12 Programming and testing of One Time PROM version
(1) 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 k
resistance.
The mask ROM version track of CNVss pin has no operational interference even if it is connected
via a resistor.
3.3.17 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 located too far from the pins to be
connected, a ceramic capacitor of 0.01
F to 0.1 F is recommended.
3.3.16 Programming and test of built-in PROM version
As for in the One Time PROM version (shipped in blank), its built-in PROM can be read or programmed
with a general-purpose PROM programmer using a special programming adapter.
The programming test and screening for PROM of the One Time PROM version (shipped in blank) are not
performed in the assembly process and the following processes. To ensure reliability after programming,
performing programming and test according to the Figure 3.3.12 before actual use are recommended.
Programming with
PROM programmer
Screening (Caution)
(150
°C for 40 hours)
Verification with PROM
programmer
Functional check in
target device
The screening temperature is far higher
than the storage temperature. Never
expose to 150
°C exceeding 100 hours.
Caution:
3.3 Notes on use