XPC850ZT50BU Datasheet, PDF (12/76 Pages) Motorola, Inc – Communications Controller Hardware Specifications

Layout Practices
Part VI Bus Signal Timing
Table 6-6 provides the bus operation timing for the MPC850 at 50 MHz, 66 MHz, and 80
MHz. Timing information for other bus speeds can be interpolated by equation using the
MPC850 Electrical Specifications Spreadsheet found at http://www.mot.com/netcomm.
The maximum bus speed supported by the MPC850 is 50 MHz. Higher-speed parts must
be operated in half-speed bus mode (for example, an MPC850 used at 66 MHz must be
configured for a 33 MHz bus).
The timing for the MPC850 bus shown assumes a 50-pF load. This timing can be derated
by 1 ns per 10 pF. Derating calculations can also be performed using the MPC850 Electrical
Specifications Spreadsheet.
Table 6-6. Bus Operation Timing ¹
Num
Characteristic
50 MHz
66 MHz
80 MHz
Cap Load
FFACT (default Unit
Min Max Min Max Min Max
50 pF)
B1 CLKOUT period
20 — 30.30 — 25 —
—
—
ns
B1a EXTCLK to CLKOUT phase
-0.90 0.90 -0.90 0.90 -0.90 0.90 —
skew (EXTCLK > 15 MHz and
MF <= 2)
50.00
ns
B1b EXTCLK to CLKOUT phase
-2.30 2.30 -2.30 2.30 -2.30 2.30 —
skew (EXTCLK > 10 MHz and
MF < 10)
50.00
ns
B1c CLKOUT phase jitter (EXTCLK -0.60 0.60 -0.60 0.60 -0.60 0.60 —
> 15 MHz and MF <= 2) ²
B1d CLKOUT phase jitter ²
-2.00 2.00 -2.00 2.00 -2.00 2.00 —
50.00
ns
50.00
ns
B1e CLKOUT frequency jitter (MF < — 0.50 — 0.50 — 0.50 —
10) ²
50.00
%
B1f CLKOUT frequency jitter (10 < — 2.00 — 2.00 — 2.00 —
MF < 500) ²
50.00
%
B1g CLKOUT frequency jitter (MF > — 3.00 — 3.00 — 3.00 —
500) ²
B1h Frequency jitter on EXTCLK ³ — 0.50 — 0.50 — 0.50 —
50.00
%
50.00
%
B2 CLKOUT pulse width low
8.00 — 12.12 — 10.00 —
—
50.00
ns
B3 CLKOUT width high
8.00 — 12.12 — 10.00 —
—
50.00
ns
B4 CLKOUT rise time
— 4.00 — 4.00 — 4.00 —
50.00
ns
B5 CLKOUT fall time
— 4.00 — 4.00 — 4.00 —
50.00
ns
B7 CLKOUT to A[6–31],
RD/WR, BURST, D[0–31],
DP[0–3] invalid
5.00 — 7.58 — 6.25 — 0.250 50.00
ns
B7a CLKOUT to TSIZ[0–1], REG, 5.00 — 7.58 — 6.25 — 0.250 50.00
ns
RSV, AT[0–3], BDIP, PTR invalid
12
MPC850 (Rev. A/B/C) Hardware Specifications
MOTOROLA