HD64F2145 Datasheet, PDF (775/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

28.2.7 Usage Notes
1. Both of the F-ZTAT version and masked-ROM version products satisfy the electrical
characteristics described in this manual, however, due to the differences in the manufacturing
process, on-chip ROMs, or layout patterns, the actual electrical characteristics, operation
margin, and noise margin may be changed.
When the F-ZTAT version was used for system evaluation, and switching from the F-ZTAT
version to the mask-ROM version is made, the equivalent evaluation should be performed for
the mask-ROM version.
2. Internal step-down products
The H8S/2148 B-masked product (HD64F2148B) includes an internal step-down circuit to
step down the microprocessor internal power supply voltage to the appropriate level.
One or two (in parallel) internal voltage regulating capacitors (0.47 µF) should be inserted
between the internal step-down pin (VCL pin) and VSS pin. The method of connecting the
external capacitor(s) is shown in figure 27-31.
For the 5-V and 4-V version products whose power supply (VCC) voltage exceeds 3.6 V, do
not connect the VCC power supply to the VCL pin of the internal step-down product.
(Connect the VCC power supply to the VCC1 pin, as usual.)
For the 3-V version product whose power supply (VCC) voltage is 3.6 V or less, connect the
system power supply to the VCL pin together with the VCC1 pins.
When switching from the F-ZTAT version product without the internal step-down function to
the F-ZTAT B-masked product with the internal step-down function, note that the VCL pin is
allocated to the same location as the VCC2 pin of the product without the internal step-down
function. Therefore, the difference in the circuits between before and after the switchover
should be considered when designing the PC board patterns.
Rev. 2.0, 08/02, page 735 of 788