Motorola MPC860 PowerQUICC, Руководство пользователя, Страница: 862 / 1106

33-2 MPC860 PowerQUICC UserÕs Manual MOTOROLA
Part V. The Communications Processor Module
Figure 33-1 is a block diagram of the PIP.
Figure 33-1. PIP Block Diagram
33.2 Core Control vs. CP Control
The host-control bit in the PIP conÞguration register PIPC[HSC] determines whether the
PIP transfer is controlled by the CP or by the core.
33.2.1 Core Control
When the PIP is controlled by the core (PIPC[HSC] = 1), only the interlocked and pulsed
handshaking modes can be used. The CP does not directly participate in the transfer, but an
Rx or Tx character event (RCH or TCH) is ßagged in the event register (PIPE). The PIPE
is then masked against the PIP mask register (PIPM); unmasked events interrupt the core.
¥ When the PIP is conÞgured to receive and STB is asserted on STBI (strobe-in on
PB14), PIPE[RCH] is set to indicate that a character has arrived. When software
reads the port B data register (PBDAT), the PIP asserts ACK through STBO
(strobe-out on PB15).
¥ When the PIP is conÞgured to send and the core writes PBDAT, STB is driven low
on STBO (strobe-out on PB15). When the destination device drives ACK low onto
STBI (strobe-in on PB14), the PIP indicates that a character was successfully sent
by ßagging PIPE[TCH].
For a core-controlled PIP, only the PIPC, PIPE, PIPM and port B registers need to be
conÞgured or monitored. The PIP parameter RAM and buffer descriptors are not used.
33.2.2 CP Control
When the PIP is controlled by the CP (PIPC[HSC] = 0), any of the three handshake modes
can be used. Data is prepared by the core using PIP buffer descriptors. CP-controlled
Port B Signals
Peripheral Bus
Handshake
U-Bus
Control
PIP Data Register
PIP Mask Register (PIPM)
PIP Event Register (PIPE)
Port B Open Drain Register (PBODR)
Port B Pin Assignment Register (PBPAR)
Port B Data Direction (PBDIR)
Timing Parameters Register (PTPR)
PIP ConÞguration Register (PIPC)