NEC PD754144 - Manual (Page 183)

CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
183 User’s Manual U10676EJ3V0UM
6.5.3 Programmable threshold port application
(1) An analog input voltage input to the PTH00 pin is A/D converted with 4-bit resolution.
Figure 6-51. Application Example of Programmable Threshold Port
PTH00 input voltage
Reference voltage (V REF )
AV REF
7.5/16 ⋅ AV
REF
V SS
Conversion
start Conversion
end
Comparison result 1 0 1 0
The conversion result is stored in bit sequential buffer BSB0 (refer to 6.6 Bit Sequential
Buffer).
ADCONV: SET MBE
SEL MB15
MOV HL, #0D3H ; H ← higher 4 bits of PTH0, L ← bit 3 specification
MOV XA, #0C0H
MOV BSB0, A ; BSB0
← 0
LOOP: SET1 BSB0, @L
MOV A, BSB0
MOV PTHM, XA ; Comparison start
MOV A, #04H ; 36-machine-cycle wait
WAIT: INCS A
BR WAIT
MOV1 CY, @H+PTH0.0 ; Conversion result input
MOV1 BSB0, @L, CY ; Conversion result store
DECS L
BR LOOP
; Conversion end