stack = $0100

screen = $0400
rowlen = $28

bdcol = $D020
bgcol = $D021

inputa = $DC00
inputb = $DC01

ch1_freq_lo = $D400
ch1_freq_hi = $D401 
ch1_duty_lo = $D402
ch1_duty_hi = $D403
ch1_ctl     = $D404
ch1_env_ad  = $D405
ch1_env_sr  = $D406