Samsung MSYS 5150, Руководство по обслуживанию

Страница: 55 / 210

Circuit Description
Samsung Electronics 5-7
ENGINE CONTROLLER
• Message Communication
The print interface uses CnPMSG and CnEMSG to
transmit and receive 8-bit message, CnPBSY and
CnEBSY to indicate the direction of data transfer and
COMCLK to pace data transmissions. PIFC does not
employ handshaking, but asserts CnPBSY and
CnEBSY before the actual data transmission to
provide sufficient time for the logic to prepare for the
subsequent data.
COMCLK remains inactive until either CnPBSY or
CnEBSY is asserted and then goes through eight
periods for 8-bit data transmission or reception.
Three registers, TBR (Transmit Buffer Register), RBR
(Receive Buffer Register), are used for message
communication. The TBR and RBR contain the 8-bit
command to be transmitted to the printer engine
through the CnEMSG pin and the 8-bit engine
message received for the printer engine through the
Cnemsg pin, respectively. The CMOD contain a
transmit enable bit (TX) to make CnPSBY signal
active, a read-only status bit (RX) to indicate the
Cnebsy signal status and 5-bit prescaler value used to
generate COMCLK clock. In message reception, the
RX bit is cleared when a low-to-high transition occurs
on CnEBSY, and at the meantime an interrupt signal
INT_BUSY is posted to indicate that one-byte engine
message has been received by PIFC.