#target TZX

0x12: Pure tone

Most #tzx directives create TZX file blocks which do not encode a Assembler directives: #code
Including C Source Files: #code#code block. You can either use the symbolic name of a TZX file block, e.g. PURE-TONE or the hexadecimal number, e.g. 0x12.

#tzx PURE-TONE, [COUNT=]num_pulses, [PULSE=]cc_per_pulse

TZX block 0x12 can be used to "manually" create a pilot tone. The pulse length is measured in ZX Spectrum clock cycles. (3.5MHz)

COUNT: Number of pulses

PULSE: Length of each pulse expressed in T-states.