Freescale Semiconductor MPC8260 - Manual (Page 668)

SDMA Channels and IDMA Emulation
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
19-24 Freescale Semiconductor
transfer sizes allows longer transfers to memory devices, optimizes bus usage and thus reduces the overall
load on the CP.
For example, 2,016 bytes can be transferred by issuing one START _ IDMA command using a 2-Kbyte
internal transfer buffer, or by issuing 63 START _ IDMA commands using a 64-byte buffer. The load on the
CP in the second case is about 63 times more than the first.
19.8.4 IDMA Event Register (IDSR) and Mask Register (IDMR)
The IDMA event (status) register (IDSR) is used to report events recognized by the IDMA controller. On
recognition of an event, the controller sets the corresponding IDSR bit. Each IDMA event bit can generate
a maskable interrupt to the core. Even bits are cleared by writing ones; writing zeros has no effect.
The IDMA mask register (IDMR) has the same format as IDSR. Setting IDMR bits enables, and clearing
IDMR bits disables, the corresponding interrupts in the event register.
Figure 19-10 shows the bit format for IDSR and IDMR.
Table 19-9 describes IDSR/IDMR fields.
19.8.5 IDMA BDs
Source addresses, destination addresses, and byte counts are presented to the CP using the special IDMA
BDs. The CP reads the BDs, programs the SDMA channel, and notifies the core about the completion of
a buffer transfer using the IDMA BDs. This concept is similar to the one used for the serial controllers on
the PowerQUICC II except that the BD is larger because it contains additional information.
0 3 4 5 6 7
Field — SC OB EDN BC
Reset 0000_0000
R/W R R/W
Addr 0x0x11020 (IDSR1), 0x0x11028 (IDSR2), 0x0x11030 (IDSR3), 0x0x11038 (IDSR4)/
0x0x11024 (IDMR1), 0x0x1102C (IDMR2), 0x0x11034 (IDMR3), 0x0x1103C (IDMR4)
Figure 19-10. IDMA Event/Mask Registers (IDSR/IDMR)
Table 19-9. IDSR/IDMR Field Descriptions
Bits Name Description
0–3 — Reserved, should be cleared.
4 SC Stop completed. Set after the IDMA channel completes processing the STOP _ IDMA command. Do
not change channel parameters until SC is set.
5 OB Out of buffers. Set to indicate that the IDMA channel encountered no valid BDs for the transfer.
6 EDN External DONE was asserted by device. Set to indicate that the IDMA channel terminated a transfer
because DONE was asserted by an external device, on the former SDMA transaction.
7 BC BD completed. Set only after all data of a BD whose I (interrupt) bit is set has completed transfer to
the destination.