18-22
MPC8260 PowerQUICC II UserÕs Manual
MOTOROLA
Part IV. Communications Processor Module
18.8.3 IDMA Performance
The transfer parameters STS, DTS, SS_MAX, and DMA_WRAP determine the amount of
data transferred for each
START
_
IDMA
command issued. Using large internal IDMA
transfer buffers and the maximum 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 Þrst.
18.8.4 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 18-9 shows the bit format for IDSR and IDMR.
011
512
15 * 32
01
15 * 32
1, 2, 4, 8 (single); 32
(burst)
10
1, 2, 4, 8 (single); 32
(burst)
15 * 32
100
1024
31 * 32
01
31 * 32
1, 2, 4, 8 (single); 32
(burst)
10
1, 2, 4, 8 (single); 32
(burst)
31 * 32
101
2048
63 * 32
01
63 * 32
1, 2, 4, 8 (single); 32
(burst)
10
1, 2, 4, 8 (single); 32
(burst)
63 * 32
1
These values come out as a single transaction on the bus.
2
Peripherals that can accept bursts of 32 bytes are supported.
Table 18-8. Valid STS/DTS Values for Peripherals (Continued)
DMA_WRAP Internal Buffer Size SS_MAX
S/D Mode
STS (in Bytes)
DTS (in Bytes)
Summary of Contents for MPC8260 PowerQUICC II
Page 1: ...MPC8260UM D 4 1999 Rev 0 MPC8260 PowerQUICC II UserÕs Manual ª ª ...
Page 66: ...lxvi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA ...
Page 88: ...1 18 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 120: ...2 32 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 138: ...Part II iv MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II Configuration and Reset ...
Page 184: ...4 46 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II ConÞguration and Reset ...
Page 202: ...Part III vi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
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Page 430: ...Part IV viii MOTOROLA Part IV Communications Processor Module ...
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Page 980: ...A 4 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Appendixes ...
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