Texas Instruments TMS320C3 Series, User Manual, Page: 152 / 166

Host Interface Control Design Notes
B-12
; If T0=T1 the output is a DC level proportional to the phase difference
;
; T0 ––––––______––––––______––––––______––––––______––––––______––––––____
; T1 ––––______––––––______––––––______––––––______––––––______––––––______
; XOR____––____––____––____––____––____––____––____––____––____––____––____
;
; USING THE PWM AS A TRIANGLE WAVE GENERATOR
; ––––––––––––––––––––––––––––––––––––––––––
; If T0 and T1 are set to different frequencies a PWM modulated triangle
; wave at a frequency of F0_t0 – F1_t1 is produced. Since the two XOR
; outputs are compliments a bridged output is created. This then allows the
; current in the LED to reverse resulting in an ; alternating color sequence
; of R–Y–G–Y–R–Y–G–Y...
;
; If T0!=T1 the output is a continuous triangle wave
;
; T0 ––––––______––––––______––––––______––––––______––––––______––––––____
; T1 –––––_____–––––_____–––––_____–––––_____–––––_____–––––_____–––––_____
; XOR_____–____––___–––__––––_––––––––––_––––__–––___––____–__________–____
;
; If an H bridge drive circuit is used with these signals an AC motor can
; be driven with an DSP controlled frequency. By using an external PAL to
; provide additional references signals and phase detectors a 3–phase PWM
; driver can be easily constructed. In this case the external PAL would
; contain a counter whose output is decoded to provide one of the reference
; frequencies in three phases seperated by 2*pi/3 radians. By then using
; one of the DSP timers for the other reference a variable frequency
; 3 phase output can be constructed.
;
; NOTE: The amplitude of the PWM triangle wave cannot be controlled from
; the timers alone. Either the DSP would have to continuously
; calculate the ouptuts as a DC reference or an external circuit
; would have to chop the output.
;––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
;
; STRB Q0
; A23 | H1 VCC| Q1
; | | | | | |
; /––––+––+––+––+––+––+––+–––+
; | 4 3 2 1 28 27 26 |
; | |
; A22–|5 25|–UW
; A21–|6 24|–UX
; A20–|7 23|–SRAM
; |8 22|
; DEMO–|9 21|–RDY
; TCK1–|10 20|–INT2
; TCK0–|11 19|–UBOOT
; | |
; | 12 13 14 15 16 17 18 |
; +––––+––+––+––+––+––+––+–––+
; | | | | | |
; R/W |GND HPS |HPA
; TRI UR
;