Hardware manual

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4. H8S/2638 microcontroller.
4.1. Overview.
H8S/2638 is microcomputer unit (MCU) employed by Renesas Technology. In general it is 32-bit
architecture unit with sixteen 16-bit general registers which can be used as 8-bit registers or as
eight 32-bit registers. The maximum clock speed of this microcontroller is 20MHz what is
comparable with the maximum speed of Intel's 80286 microprocessor. Of course we can't make
such comparisons, but I think it is very good way how to imagine speed limitation or slowness of
this microcontroller. Available address size allows using 16-Mbyte address space which seems to
be enough for most of the basic tasks as for example motor control.
Fig. 4.1-1. H8S/2638
H8S/2638 has built in16kbytes of RAM and 256kbytes of mask ROM or flash memory. Because
ROM can work in this specification as flash memory, so it is possible to upload once software
and then use it every time when we switch on the power for microcontroller.
Additionally, H8S/2638 has watchdog timer, serial communication interface, A/D and D/A
converters and CAN (Controller Area Network) bus controller. Except of that, H8S/2638 has built
in time-pulse unit (TPU), programmable pulse generator (PPG) and motor control PWM timer.
This last functionality is very useful always when we want to use this device for motion control
of some motor.