Serial Interface
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
20-29
There are two definitions of the IDL bus frame structure—8- and 10-bit. The only difference between them
is the channel order within the frame. See
Figure 20-26
.
Figure 20-26. IDL Bus Signals
Note that previous versions of Motorola IDL-defined bit functions called auxiliary (A) and maintenance
(M) were removed from the IDL definition when it was concluded that the IDL control channel would be
out-of-band. These functions were defined as a subset of the Motorola SPI format called serial control port
(SCP). To implement the A and M bits as originally defined, program the TSA to access these bits and
route them transparently to an SCC or SMC. Use the SPI to perform out-of-band signaling.
The MPC885 supports all channels of the IDL bus in the basic rate. Each bit in the IDL frame can be routed
to any SCC and SMC or they can assert a strobe output that supports an external device.
The MPC885 supports the request-grant method for contention detection on the D channel of the IDL basic
rate and when the MPC885 has data to send on the D channel, it asserts L1RQx. The physical layer device
monitors the physical layer bus for activity on the D channel and indicates that the channel is free by
asserting L1GRx. The MPC885 samples L1GRx when the IDL sync signal (L1RSYNCx) is asserted. If
L1GRx is asserted, the MPC885 sends the first zero of the opening flag in the first bit of the D channel. If
a collision is detected on the D channel, the physical layer device negates L1GRx. The MPC885 then stops
its transmission and resends the frame when L1GRx is reasserted. This procedure is handled automatically
for the first two buffers of a frame.
For the primary rate IDL, the MPC885 supports up to four 8-bit channels in the frame, determined by the
SI RAM programming. Additionally, the MPC885 can assert strobes to support additional external IDL
channels. The IDL interface supports the CCITT I.460 recommendation for data rate adaptation since it
separately accesses each bit of the IDL bus. The current-route RAM specifies the bits that are supported
by the IDL interface and the serial controller. The receiver accepts only the bits enabled by the Rx route
RAM. Likewise, the transmitter sends only the bits enabled in the Tx route RAM and three-states L1TXDx.
L1CLK
L1SYNC
L1RXD
L1TXD
B1
D1
10-Bit IDL
D2
B1
D1
B2
D2
L1RXD
L1TXD
B1
D1
8-Bit IDL
D2
B1
B2
D2
B2
D1
B2
Notes:
1. Clocks are not to scale.
2. L1RQ
x and L1GRx are not shown.
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...