H8S2199R Datasheet, PDF (719/1222 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2100 Series

Section 26 Servo Circuits
26.11.7 Operations in Case of Transient Response
In case of transient response when the motor is activated, the digital filter computation circuit
must prevent computation due to a large error. The convergence of the computations becomes
slow and servo retraction deteriorates if a large error is input to the filter circuit when it is
performing repeated computations. To prevent them from occurring, operate the filter (set
constants A and B) after pulling in the speed and phase within a certain range of error, initialize
the Z^-1 (set initial values in CZp, CZs, DZp, DZs)(see section 26.11.8, Initialization of Z^-1), or use
the error data limit function (see section 26.6, Drum Speed Error Detector, and section 26.8,
Capstan Speed Error Detector).
26.11.8 Initialization of Z^-1
Z^-1 can be initialized by its delay initialization register (CZp, CZs, DZp, DZs). Loading to Z^-1 is
performed automatically by bits 4 and 3 of CFIC and DFIC (CZPON, CZSON, DZPON,
DZSON). Writing in register is always available, but loading in Z^-1 is not possible when the digital
filter is performing computation in relation to such register. In such a case, loading to Z^-1 will be
done when the next time computation begins. Figure 26.42 shows the initialization circuit of Z^-1.
The delay initialization register sets 12-bit data. The MSB (bit 11) is a sign bit. Z^-1 has 24 bits for
integrals and 8 bits for decimals. Accordingly, the same value as the sign bit should be set in the
13 bits on the MSB side of Z^-1, and 0 in the entire decimal section.
Example: Value set for the delay initialization register
Value set for Z^-1
MSB
MSB
100000000000
111111111111100000000000
00000000
Set here the value in the
sign bit
Fixed
Rev.2.00 Jan. 15, 2007 page 675 of 1174
REJ09B0329-0200