Pin for Pin Compatibility of DM357 and DM644x

Overview

The DM644x family of processors has several pin-for-pin compatible variants: DM6446, DM6443, DM6441. To further enhance the selection of pin-for-pin compatible devices another device was created to be pin-for-pin compatible with these existing parts. That device is the DM357.

Pin-for-pin compatibility has some great advantages:

• A design can easily upgrade, e.g. from DM357 to DM6446 without any hardware changes!
• A "common platform" can be used such that the same board is being used across multiple designs.
  • Reduces hardware development time
  • Increases driver/software re-use

Comparison of Devices

Key Differences between DM357 and DM644x

• DM357 has 270 MHz ARM rather than 297 MHz on DM6446
• DM357 has H.264/MPEG-4/JPEG accelerator rather than DSP and VICP
• DM357 has 3 DACs, not 4
• DM357 does not have CF/ATA interface
• DM357 does not have VLYNQ
• DM357 requires Ball B17 be pulled down. That would correspond to the DSP being held in reset and booted by the ARM on the DM644x devices, which is typically the way it would be used anyway.

	DM6446	DM6443	DM6441	DM357
ARM926EJ-S Speed	297 MHz	297 MHz	256 MHz	270 MHz
ARM9 Cache($)/Memory	16KB I$, 8KB D$, 16KB RAM	16KB I$, 8KB D$, 16KB RAM	16KB I$, 8KB D$, 16KB RAM	16KB I$, 8KB D$, 16KB RAM
Coprocessors	DSP, VICP	DSP	DSP, VICP	H.264/MPEG-4/JPEG accel.
Video Processing Front End	YES	NO	YES	YES
Video Processing Back End	YES, 4 DACs	YES, 4 DACs	YES, 4 DACs	YES, 3 DACs
EMAC	10/100	10/100	10/100	10/100
USB	2.0 OTG	2.0 OTG	2.0 OTG	2.0 OTG
SD/MMC	YES	YES	YES	YES
CF/ATA	YES	YES	YES	NO
VLYNQ	YES	YES	YES	NO
UART	3 (1 with flow control)	3 (1 with flow control)	3 (1 with flow control)	3 (1 with flow control)
GP Timer	2x 64-bit	2x 64-bit	2x 64-bit	2x 64-bit
Watchdog	1x 64-bit	1x 64-bit	1x 64-bit	1x 64-bit
I2C	YES	YES	YES	YES
SPI	YES	YES	YES	YES
PWM	3	3	3	3
HPI	16-bit muxed	16-bit muxed	16-bit muxed	16-bit muxed
EDMA3	64-channel	64-channel	64-channel	64-channel
DDR2	32-bit, 125-166.67 MHz	32-bit, 125-166.67 MHz	32-bit, 125-166.67 MHz	32-bit, 125-166.67 MHz
EMIFA	16-bit (NAND/NOR)	16-bit (NAND/NOR)	16-bit (NAND/NOR)	16-bit (NAND/NOR)
Audio Serial Port	YES	YES	YES	YES
GPIO	71	71	71	71
Package	361-pin BGA (0.8mm spacing)	361-pin BGA (0.8mm spacing)	361-pin BGA (0.8mm spacing)	361-pin BGA (0.8mm spacing)
Temp Options	0-85°C, -40-85°C	0-85°C	0-85°C	0-85°C
Price (100u as of 4/15/2009)	$39.35	$33.75	$34.00	$20.20

Software Compatibility

No software changes should be required when sharing code between DM6446 and DM357. The peripheral layout (memory map) is identical aside from the peripherals that were removed in DM357 (i.e. VLYNQ, a DAC, CF/ATA, DSP). In terms of using the codecs, the Codec Engine framework isolates the end user from changes "under the hood" that result from removing the DSP and adding the HMJCP.

For example, if you had a high-end platform using DM6446 and a lower cost platform using DM357 you could have basic encode/decode functionality on both platforms using the exact same APIs. If you wished to add custom image processing analytics to the DSP you would have that flexibility on the DM6446.