SHARP_LH7A404 Datasheet, PDF (38/51 Pages) Sharp Electrionic Components – 32 BIT SYSTEM ON CHIP

LH7A404
32-Bit System-on-Chip
SSP Waveforms
The Synchronous Serial Port (SSP) supports three
data frame formats:
• Texas Instruments’ synchronous serial
• Motorola SPI
• National Semiconductor MICROWIRE
Each frame format is between 4 and 16 bits in
length, depending upon the programmed data size.
Each data frame is transmitted beginning with the Most
Significant Bit (MSB) i.e. ‘big endian’. For all three for-
mats, the SSP serial clock is held LOW (inactive) while
the SSP is idle. The SSP serial clock transitions only
during active transmission of data. The SSPFRM sig-
nal marks the beginning and end of a frame. The
SSPEN signal controls an off-chip line driver’s output
enable pin.
Figure 12 and Figure 13 show Texas Instruments
synchronous serial frame format, Figure 14 through
Figure 21 show the Motorola SPI format, and Figure 22
and Figure 23 show National Conductor’s MICRO-
WIRE data frame format.
For Texas Instruments’ synchronous serial frame for-
mat, the SSPFRM pin is pulsed prior to each frame’s
transmission for one serial clock period beginning at its
rising edge. For this frame format, both the SSP and the
external slave device drive their output data on the ris-
ing edge of the clock and latch data from the other
device on the falling edge. See Figure 12 and Figure 13.
SSPCLK
SSPFRM
SSPTXD/
SSPRXD
MSB
LSB
4 to 16 BITS
LH7A404-24
Figure 12. Texas Instruments Synchronous Serial Frame Format (Single Transfer)
SSPCLK
SSPFRM
SSPTXD/
SSPRXD
MSB
LSB
4 to 16 BITS
LH7A404-25
Figure 13. Texas Instruments Synchronous Serial Frame Format (Continuous Transfer)
38
Advance Data Sheet