z16f2811 ZiLOG Semiconductor, z16f2811 Datasheet - Page 191

• Manufacturer Part Number: z16f2811
• Description: High Performance Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS022006-0207
Throughput
ESPI Clock Phase and Polarity Control
ESPIEN1, 0 bits in the control register to
move the data, the transmit and receive data interrupts are disabled through the DIRQE bit
of the control register. In this case error interrupts still occurs and must be handled directly
by the software.
In MASTER mode the maximum SCK rate supported is one-half the system clock
frequency. This is achieved by programming the value 0001H into the baud rate high/low
register pair. Though each character is transferred at this rate, it is unlikely that software
interrupt routines or DMA keeps up with this rate. In SPI mode the transfer will
automatically pause between characters until the current receive character is read and the
next transmit data value is written.
In SLAVE mode, the transfer rate is controlled by the master. As long as the TDRE and
RDRF interrupt or DMA requests are serviced before the next character transfer completes
the slave will keep up with the master. In SLAVE mode, the baud rate is restricted to a
maximum of one-fourth of the system clock frequency to allow for synchronization of the
SCK input to the internal system clock.
The ESPI supports four combinations of SCK phase and polarity using two bits in the
ESPI control register. The clock polarity bit, CLKPOL, selects an active high or active low
clock and has no effect on the transfer format. The clock phase bit, PHASE, selects one of
two fundamentally different transfer formats. The data is output a half-cycle before the
receive clock edge which provides a half cycle of setup and hold time.
ESPI clock phase and polarity operation parameters.
Table 94. ESPI Clock Phase (PHASE) and Clock Polarity (CLKPOL) Operation
Transfer Format with Phase Equals Zero
Figure 35
PHASE =
SCK waveforms show polarity with CLKPOL =
PHASE
0
0
1
1
0
on page 178 illustrates the timing diagram for an SPI type transfer in which
. For SPI transfers the clock only toggles during the character transfer. The two
CLKPOL
0
1
0
1
P R E L I M I N A R Y
SCK Transmit
Falling
Falling
Rising
Rising
Edge
10
or
01
0
and with CLKPOL =
. If the DMA engine is being used to
Enhanced Serial Peripheral Interface
SCK Receive
Falling
Falling
Rising
Rising
Edge
Product Specification
ZNEO
Table 94
1
. The diagram is
™
SCK Idle
Z16F Series
State
High
High
Low
Low
lists the
177