19 UNIVERSAL SERIAL INTERFACE WITH LCD INTERFACE (USIL)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
19-31
Interrupts in LCD SPI Mode
19.7.5
The LCD SPI mode includes a function for generating the following interrupt.
• Transmit buffer empty interrupt
Transmit buffer empty interrupt
To use this interrupt, set LSTDIE/USIL_LSIE register to 1. If LSTDIE is set to 0 (default), interrupt requests
for this cause will not be sent to the ITC.
When transmit data written to the transmit data buffer is transferred to the shift register, the USIL module sets
LSTDIF/USIL_LSIF register to 1, indicating that the transmit data buffer is empty. If transmit buffer empty
interrupts are enabled (LSTDIE = 1), an interrupt request is sent simultaneously to the ITC. An interrupt occurs
if other interrupt conditions are met. You can inspect the LSTDIF flag in the interrupt handler routine to deter-
mine whether the USIL (LCD SPI mode) interrupt is attributable to a transmit buffer empty. If LSTDIF is 1, the
next transmit data can be written to the transmit data buffer by the interrupt handler routine.
Interrupts in LCD Parallel Mode
19.7.6
The LCD parallel mode includes a function for generating the following two different types of interrupts.
• Write buffer empty interrupt
• Read buffer full interrupt
Write buffer empty interrupt
To use this interrupt, set LPWRIE/USIL_LPIE register to 1. If LPWRIE is set to 0 (default), interrupt requests
for this cause will not be sent to the ITC.
When data written to the write (transmit data) buffer is output via the LCD_D[7:0] pins , the USIL module sets
LPWRIF/USIL_LPIF register to 1, indicating that the write buffer is empty. If write buffer empty interrupts are
enabled (LPWRIE = 1), an interrupt request is sent simultaneously to the ITC. An interrupt occurs if other inter-
rupt conditions are met. You can inspect the LPWRIF flag in the interrupt handler routine to determine whether
the USIL (LCD parallel mode) interrupt is attributable to a write buffer empty. If LPWRIF is 1, the next data
can be written to the write buffer by the interrupt handler routine.
Read buffer full interrupt
To use this interrupt, set LPRDIE/USIL_LPIE register to 1. If LPRDIE is set to 0 (default), interrupt requests
for this cause will not be sent to the ITC.
If data sent from the LCD driver/panel is loaded into the read (receive data) buffer, the USIL module sets LPR-
DIF/USIL_LPIF register to 1. If read buffer full interrupts are enabled (LPRDIE = 1), an interrupt request is
sent simultaneously to the ITC. An interrupt occurs if other interrupt conditions are met. You can inspect the
LPRDIF flag in the interrupt handler routine to determine whether the USIL (LCD parallel mode) interrupt is
attributable to a read buffer full. If LPRDIF is 1, data can be read from the read buffer by the interrupt handler
routine.
DMA Transfer
19.7.7
The causes of receive (read) buffer full and transmit (write) buffer empty interrupts in UART, SPI master/slave,
LCD SPI, and LCD parallel modes can invoke a DMA. This allows continuous data transmission/reception through
DMA transfer between memory and transmit/receive data buffers. These interrupt signals are output to both the ITC
and DMAC. Therefore, DMA transfer can be performed without generating any USIL interrupt.
The following lists the DMAC channels that allow selection of a USIL interrupt cause as the trigger.
USIL receive (read) buffer full:
DMAC Ch.6
USIL transmit (write) buffer empty: DMAC Ch.7
For more information on DMA transfer, see the “DMA Controller (DMAC)” chapter.
Note: The USIL module cannot invoke a DMA in I
2
C master and slave mode.