Hitachi H8S/2199 Hardware Manual page 582

Field signal
VD
Selected VD
(OD/EV=0)
Value set in reference
period register 1 (RFD)
Counter
Value set in REF30
counter register (RFC)
Masking
Toggle mask
period
Counter mask
Masking
period
(clear signal mask)
About 75%
REF30
REF30P
HSW
Drum phase counter
T
Sampling Sampling
Sampling
Figure 26.9 Generation of Reference Signal in Record Mode (Normal Operation)
Rev. 1.0, 02/00, page 576 of 1141