M30218 Datasheet, PDF (66/179 Pages) Mitsubishi Electric Semiconductor – M30218 Group

FLD controller
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
FLD automatic display start
Automatic display starts by setting both the automatic display control bit (bit 0 of address 035016) and the
display start bit (bit 1 of address 035016) to “1”. The RAM content at a location apart from the start address
of the automatic display RAM for each port by (FLD data pointer (address 035816) – 1) is output to each
port. The FLD data pointer (address 035816) counts down in the Tdisp interval. When the count “FF16” is
reached, the pointer is reloaded and starts counting over again. Before setting the display start bit (bit 1 of
address 035016) to “1”, be sure to set the FLD/port switch register, FLD/DIG switch register, FLDC mode
register, Tdisp time set register, Toff1 time set register, Toff2 time set register, and FLD data pointer.
During FLD automatic display, bit 1 of the FLDC mode register (address 035016) always keeps “1”, and
FLD automatic display can be interrupted by writing “0” to bit 1.
Key-scan and interrupt
Either a FLD digit interrupt or FLD blanking interrupt can be selected using the Tscan control bits (bits 2, 3
of address 035016).
The FLD digit interrupt is generated when the Toff1 time in each timing expires (at rising edge of digit
output). Key scanning that makes use of FLD digits can be achieved using each FLD digit interrupt. To use
FLD digit interrupts for key scanning, follow the procedure described below.
(1) Read the port value each time the interrupt occurs.
(2) The key is fixed on the last digit interrupt.
The digit positions output can be determined by reading the FLD data pointer (address 035816).
Repeat synchronous
Tdisp
Toff1
FLD digit output
Tn Tn-1 Tn-2
T4 T3 T2 T1 Tn Tn-1 Tn-2
T4
FLD digit interrupt generated at the rising edge of digit ( each timing)
Figure KA-12A. Timing using digit interrupt
65